diff --git a/client/src/components/Dataset/DatasetAsImage/DatasetAsImage.vue b/client/src/components/Dataset/DatasetAsImage/DatasetAsImage.vue
index 1b7e19e201c..bf1ac33c718 100644
--- a/client/src/components/Dataset/DatasetAsImage/DatasetAsImage.vue
+++ b/client/src/components/Dataset/DatasetAsImage/DatasetAsImage.vue
@@ -1,6 +1,10 @@
 <template>
     <div>
-        <img v-if="imgUrl" :src="imgUrl" />
+        <div v-if="imageUrl" class="w-50 p-2 float-left">
+            <b-card nobody body-class="p-1">
+                <b-img :src="imageUrl" fluid />
+            </b-card>
+        </div>
         <div v-else>
             <b>Image is not found</b>
         </div>
@@ -26,13 +30,13 @@ export default {
         if (this.path) {
             this.fetchPathDestination({ history_dataset_id: this.history_dataset_id, path: this.path }).then(() => {
                 const pathDestination = this.$store.getters.pathDestination(this.history_dataset_id, this.path);
-                this.imgUrl = pathDestination.fileLink;
+                this.imageUrl = pathDestination.fileLink;
             });
-        } else this.imgUrl = `${getAppRoot()}dataset/display?dataset_id=${this.history_dataset_id}`;
+        } else this.imageUrl = `${getAppRoot()}dataset/display?dataset_id=${this.history_dataset_id}`;
     },
     data() {
         return {
-            imgUrl: undefined,
+            imageUrl: undefined,
         };
     },
     methods: {
diff --git a/client/src/components/Markdown/Elements/HistoryDatasetAsImage.vue b/client/src/components/Markdown/Elements/HistoryDatasetAsImage.vue
index 2fa2a06915d..ddbda951731 100644
--- a/client/src/components/Markdown/Elements/HistoryDatasetAsImage.vue
+++ b/client/src/components/Markdown/Elements/HistoryDatasetAsImage.vue
@@ -1,8 +1,6 @@
 <template>
-    <div class="w-50 p-2 float-left">
-        <b-card nobody body-class="p-1">
-            <b-img :src="imageUrl" fluid />
-        </b-card>
+    <div>
+        <DatasetAsImage :path="args.path" :history_dataset_id="args.history_dataset_id" />
     </div>
 </template>
 
@@ -10,10 +8,14 @@
 import Vue from "vue";
 import BootstrapVue from "bootstrap-vue";
 import { getAppRoot } from "onload/loadConfig";
+import DatasetAsImage from "components/Dataset/DatasetAsImage/DatasetAsImage";
 
 Vue.use(BootstrapVue);
 
 export default {
+    components: {
+        DatasetAsImage,
+    },
     props: {
         args: {
             type: Object,
diff --git a/client/src/components/admin/Dependencies/ContainerIndex.vue b/client/src/components/admin/Dependencies/ContainerIndex.vue
index 26630ffd831..b87d158bd10 100644
--- a/client/src/components/admin/Dependencies/ContainerIndex.vue
+++ b/client/src/components/admin/Dependencies/ContainerIndex.vue
@@ -170,16 +170,7 @@ export default {
             return params;
         },
         selectedToolIds() {
-            const toolIds = [];
-            for (const item of this.items) {
-                if (item["selected"]) {
-                    const toolId = item["tool"];
-                    if (toolId) {
-                        toolIds.push(toolId[0]);
-                    }
-                }
-            }
-            return toolIds;
+            return this.items.filter((item) => item.selected).map((item) => item.tool_id);
         },
     },
     watch: {
diff --git a/config/plugins/visualizations/mvpapp/src/index.js b/config/plugins/visualizations/mvpapp/src/index.js
index 8c1424c1e18..616efb27d18 100644
--- a/config/plugins/visualizations/mvpapp/src/index.js
+++ b/config/plugins/visualizations/mvpapp/src/index.js
@@ -1971,7 +1971,7 @@ var PeptideView = (function (pv) {
 
         option.scoreSummary = true;
 
-        psmDetailDP = new AjaxDataProvider(option);
+        let psmDetailDP = new AjaxDataProvider(option);
         psmDetailDP.generateTable();
         //Move to table
         $("html, body").animate(
diff --git a/doc/source/releases/20.09_announce.rst b/doc/source/releases/20.09_announce.rst
index 5c766f2bc44..6881ecc1b25 100644
--- a/doc/source/releases/20.09_announce.rst
+++ b/doc/source/releases/20.09_announce.rst
@@ -54,11 +54,9 @@ The following configuration options have been changed
 New Configuration Files
 -----------------------
 
-The following files are new, or recently converted to yaml
+The following configuration file is new:
 
 -  ``config/trs_servers_conf.yml.sample``
--  ``config/build_mulled_singularity_mapping_file.yml.sample``
--  ``config/singularity_mapping.yml.sample``
 
 
 Get Galaxy
diff --git a/lib/galaxy/job_metrics/instrumenters/collectl.py b/lib/galaxy/job_metrics/instrumenters/collectl.py
index 8d0a92e7a8b..33a18063d8a 100644
--- a/lib/galaxy/job_metrics/instrumenters/collectl.py
+++ b/lib/galaxy/job_metrics/instrumenters/collectl.py
@@ -99,7 +99,7 @@ class CollectlPlugin(InstrumentPlugin):
         pid = open(self.__pid_file(job_directory)).read().strip()
         contents = os.listdir(job_directory)
         try:
-            rel_path = filter(self._is_instrumented_collectl_log, contents)[0]
+            rel_path = next(iter(filter(self._is_instrumented_collectl_log, contents)))
             path = os.path.join(job_directory, rel_path)
         except IndexError:
             message = f"Failed to find collectl log in directory {job_directory}, files were {contents}"
diff --git a/lib/galaxy/tool_util/deps/container_resolvers/mulled.py b/lib/galaxy/tool_util/deps/container_resolvers/mulled.py
index 5f919ec9645..2989b3f1b89 100644
--- a/lib/galaxy/tool_util/deps/container_resolvers/mulled.py
+++ b/lib/galaxy/tool_util/deps/container_resolvers/mulled.py
@@ -234,7 +234,7 @@ def singularity_cached_container_description(targets, cache_directory, hash_func
     return container
 
 
-def targets_to_mulled_name(targets, hash_func, namespace, resolution_cache=None):
+def targets_to_mulled_name(targets, hash_func, namespace, resolution_cache=None, session=None):
     unresolved_cache_key = "galaxy.tool_util.deps.container_resolvers.mulled:unresolved"
     if resolution_cache is not None:
         if unresolved_cache_key not in resolution_cache:
@@ -265,7 +265,7 @@ def targets_to_mulled_name(targets, hash_func, namespace, resolution_cache=None)
         if name:
             return name
 
-        tags = mulled_tags_for(namespace, target.package_name, resolution_cache=resolution_cache)
+        tags = mulled_tags_for(namespace, target.package_name, resolution_cache=resolution_cache, session=session)
 
         if tags:
             for tag in tags:
@@ -284,7 +284,7 @@ def targets_to_mulled_name(targets, hash_func, namespace, resolution_cache=None)
             else:
                 repo_name = image_name
                 tag_prefix = None
-            tags = mulled_tags_for(namespace, repo_name, tag_prefix=tag_prefix, resolution_cache=resolution_cache)
+            tags = mulled_tags_for(namespace, repo_name, tag_prefix=tag_prefix, resolution_cache=resolution_cache, session=session)
             return tags[0] if tags else None
 
         if hash_func == "v2":
@@ -388,7 +388,7 @@ class MulledDockerContainerResolver(ContainerResolver):
         command = container.build_pull_command()
         shell(command)
 
-    def resolve(self, enabled_container_types, tool_info, install=False, **kwds):
+    def resolve(self, enabled_container_types, tool_info, install=False, session=None, **kwds):
         resolution_cache = kwds.get("resolution_cache")
         if tool_info.requires_galaxy_python_environment or self.container_type not in enabled_container_types:
             return None
@@ -397,7 +397,7 @@ class MulledDockerContainerResolver(ContainerResolver):
         if len(targets) == 0:
             return None
 
-        name = targets_to_mulled_name(targets=targets, hash_func=self.hash_func, namespace=self.namespace, resolution_cache=resolution_cache)
+        name = targets_to_mulled_name(targets=targets, hash_func=self.hash_func, namespace=self.namespace, resolution_cache=resolution_cache, session=session)
         if name:
             container_id = f"quay.io/{self.namespace}/{name}"
             if self.protocol:
@@ -447,7 +447,7 @@ class MulledSingularityContainerResolver(MulledDockerContainerResolver):
         self.hash_func = hash_func
         self.auto_install = string_as_bool(auto_install)
 
-    def cached_container_description(self, targets, namespace, hash_func):
+    def cached_container_description(self, targets, namespace, hash_func, resolution_cache):
         return singularity_cached_container_description(targets,
                                                         cache_directory=self.cache_directory,
                                                         hash_func=hash_func)
diff --git a/lib/galaxy/tool_util/deps/containers.py b/lib/galaxy/tool_util/deps/containers.py
index 3a041537951..ac31b5bc3d8 100644
--- a/lib/galaxy/tool_util/deps/containers.py
+++ b/lib/galaxy/tool_util/deps/containers.py
@@ -243,7 +243,7 @@ class ContainerRegistry:
             return None
         return None if resolved_container_description is None else resolved_container_description.container_description
 
-    def resolve(self, enabled_container_types, tool_info, index=None, resolver_type=None, install=True, resolution_cache=None):
+    def resolve(self, enabled_container_types, tool_info, index=None, resolver_type=None, install=True, resolution_cache=None, session=None):
         resolution_cache = resolution_cache or self.mulled_resolution_cache
         for i, container_resolver in enumerate(self.container_resolvers):
             if index is not None and i != index:
@@ -259,7 +259,7 @@ class ContainerRegistry:
             if not install and container_resolver.builds_on_resolution:
                 continue
 
-            container_description = container_resolver.resolve(enabled_container_types, tool_info, resolution_cache=resolution_cache)
+            container_description = container_resolver.resolve(enabled_container_types, tool_info, resolution_cache=resolution_cache, session=session)
             log.info(f"Checking with container resolver [{container_resolver}] found description [{container_description}]")
             if container_description:
                 assert container_description.type in enabled_container_types
diff --git a/lib/galaxy/tool_util/deps/mulled/mulled_build_channel.py b/lib/galaxy/tool_util/deps/mulled/mulled_build_channel.py
index 31582cf7025..2651e32f071 100644
--- a/lib/galaxy/tool_util/deps/mulled/mulled_build_channel.py
+++ b/lib/galaxy/tool_util/deps/mulled/mulled_build_channel.py
@@ -22,6 +22,8 @@ import subprocess
 import sys
 import time
 
+import requests
+
 from ._cli import arg_parser
 from .mulled_build import (
     add_build_arguments,
@@ -58,6 +60,7 @@ def _new_versions(quay, conda):
 
 def run_channel(args, build_last_n_versions=1):
     """Build list of involucro commands (as shell snippet) to run."""
+    session = requests.session()
     for pkg_name, pkg_tests in get_affected_packages(args):
         repo_data = _fetch_repo_data(args)
         c = conda_versions(pkg_name, repo_data)
@@ -66,7 +69,7 @@ def run_channel(args, build_last_n_versions=1):
 
         if not args.force_rebuild:
             time.sleep(1)
-            q = quay_versions(args.namespace, pkg_name)
+            q = quay_versions(args.namespace, pkg_name, session)
             versions = _new_versions(q, c)
         else:
             versions = c
diff --git a/lib/galaxy/tool_util/deps/mulled/util.py b/lib/galaxy/tool_util/deps/mulled/util.py
index b3e68824dea..2078766b8eb 100644
--- a/lib/galaxy/tool_util/deps/mulled/util.py
+++ b/lib/galaxy/tool_util/deps/mulled/util.py
@@ -32,9 +32,9 @@ def create_repository(namespace, repo_name, oauth_token):
     requests.post("https://quay.io/api/v1/repository", json=data, headers=headers, timeout=QUAY_IO_TIMEOUT)
 
 
-def quay_versions(namespace, pkg_name):
+def quay_versions(namespace, pkg_name, session=None):
     """Get all version tags for a Docker image stored on quay.io for supplied package name."""
-    data = quay_repository(namespace, pkg_name)
+    data = quay_repository(namespace, pkg_name, session=session)
 
     if 'error_type' in data and data['error_type'] == "invalid_token":
         return []
@@ -45,11 +45,13 @@ def quay_versions(namespace, pkg_name):
     return [tag for tag in data['tags'].keys() if tag != 'latest']
 
 
-def quay_repository(namespace, pkg_name):
+def quay_repository(namespace, pkg_name, session=None):
     assert namespace is not None
     assert pkg_name is not None
     url = f'https://quay.io/api/v1/repository/{namespace}/{pkg_name}'
-    response = requests.get(url, timeout=QUAY_IO_TIMEOUT)
+    if not session:
+        session = requests.session()
+    response = session.get(url, timeout=QUAY_IO_TIMEOUT)
     data = response.json()
     return data
 
@@ -74,7 +76,7 @@ def _namespace_has_repo_name(namespace, repo_name, resolution_cache):
     return repo_name in repo_names
 
 
-def mulled_tags_for(namespace, image, tag_prefix=None, resolution_cache=None):
+def mulled_tags_for(namespace, image, tag_prefix=None, resolution_cache=None, session=None):
     """Fetch remote tags available for supplied image name.
 
     The result will be sorted so newest tags are first.
@@ -101,7 +103,7 @@ def mulled_tags_for(namespace, image, tag_prefix=None, resolution_cache=None):
             tags_cached = True
 
     if not tags_cached:
-        tags = quay_versions(namespace, image)
+        tags = quay_versions(namespace, image, session)
         tag_cache[namespace][image] = tags
 
     if tag_prefix is not None:
diff --git a/lib/galaxy/tool_util/deps/views.py b/lib/galaxy/tool_util/deps/views.py
index b5d785ea3bc..985103d159a 100644
--- a/lib/galaxy/tool_util/deps/views.py
+++ b/lib/galaxy/tool_util/deps/views.py
@@ -333,6 +333,7 @@ class ContainerResolutionView:
             'install': False,
             'enabled_container_types': ['docker', 'singularity'],
             'resolution_cache': kwds.get("resolution_cache"),
+            'session': kwds.get('session'),
         }
 
         if 'index' in kwds:
diff --git a/lib/galaxy/tools/__init__.py b/lib/galaxy/tools/__init__.py
index 02a8a34db40..df0c64fbfb7 100644
--- a/lib/galaxy/tools/__init__.py
+++ b/lib/galaxy/tools/__init__.py
@@ -2791,7 +2791,7 @@ class DatabaseOperationTool(Tool):
 
             if self.require_dataset_ok:
                 if state != model.Dataset.states.OK:
-                    raise ValueError("Tool requires inputs to be in valid state.")
+                    raise ValueError("Tool requires inputs to be in valid state, but dataset {} is in state '{}'".format(input_dataset, input_dataset.state))
 
         for input_dataset in input_datasets.values():
             check_dataset_state(input_dataset.state)
diff --git a/lib/galaxy/webapps/galaxy/api/container_resolution.py b/lib/galaxy/webapps/galaxy/api/container_resolution.py
index 5ac3fe202c1..d545c40cecf 100644
--- a/lib/galaxy/webapps/galaxy/api/container_resolution.py
+++ b/lib/galaxy/webapps/galaxy/api/container_resolution.py
@@ -3,6 +3,8 @@ API operations allowing clients to manage container resolution.
 """
 import logging
 
+import requests
+
 from galaxy.tool_util.deps import views
 from galaxy.web import (
     expose_api,
@@ -62,6 +64,7 @@ class ContainerResolutionAPIController(BaseAPIController):
         :returns:   a dictified description of the container dependency, with attribute
                     ``dependency_type: None`` if no match was found.
         """
+        kwds['session'] = requests.session()
         return self._view.resolve(index=index, **kwds)
 
     @expose_api
@@ -81,6 +84,7 @@ class ContainerResolutionAPIController(BaseAPIController):
         :rtype:     list
         :returns:   list of items returned from resolve()
         """
+        kwds['session'] = requests.session()
         return self._view.resolve_toolbox(**kwds)
 
     @expose_api
@@ -99,6 +103,7 @@ class ContainerResolutionAPIController(BaseAPIController):
         """
         kwds.update(payload)
         kwds["install"] = True
+        kwds['session'] = requests.session()
         return self._view.resolve_toolbox(**kwds)
 
     @expose_api