Probably didn't work for some time and seems unnecessary.
Fixes
```
galaxy.tool_shed.galaxy_install.installed_repository_manager DEBUG 2020-02-28 10:57:01,109 [p:94029,w:0,m:0] [MainThread] Adding an entry for version 2.2.4 of package bowtie2 to runtime_tool_dependencies_of_installed_tool_dependencies.
Traceback (most recent call last):
File "lib/galaxy/webapps/galaxy/buildapp.py", line 48, in app_factory
app = galaxy.app.UniverseApplication(global_conf=global_conf, **kwargs)
File "lib/galaxy/app.py", line 95, in __init__
self.installed_repository_manager = InstalledRepositoryManager(self)
File "lib/galaxy/tool_shed/galaxy_install/installed_repository_manager.py", line 84, in __init__
self.load_dependency_relationships()
File "lib/galaxy/tool_shed/galaxy_install/installed_repository_manager.py", line 734, in load_dependency_relationships
self.add_entry_to_runtime_tool_dependencies_of_installed_tool_dependencies(tool_dependency)
File "lib/galaxy/tool_shed/galaxy_install/installed_repository_manager.py", line 218, in add_entry_to_runtime_tool_dependencies_of_installed_tool_dependencies
status=None)
File "lib/galaxy/tool_shed/galaxy_install/installed_repository_manager.py", line 604, in get_runtime_dependent_tool_dependency_tuples
required_env_shell_file_path = tool_dependency.get_env_shell_file_path(self.app)
File "lib/galaxy/model/tool_shed_install/__init__.py", line 522, in get_env_shell_file_path
installation_directory = self.installation_directory(app)
File "lib/galaxy/model/tool_shed_install/__init__.py", line 534, in installation_directory
return os.path.join(app.tool_dependency_dir,
File "lib/galaxy/config/__init__.py", line 1186, in tool_dependency_dir
return self.toolbox.dependency_manager.default_base_path
AttributeError: 'UniverseApplication' object has no attribute 'toolbox'
```
reported by @scholtalbers
- Allow specifying Python to use to create virtualenv using GALAXY_PYTHON
environment variable.
- Integrate Python support docs from https://galaxyproject.org/admin/python/
- Update virtualenv installation to use v16.7.9
mvdbeek