Fix flake8 errors and Python3 compatibility for doc/patch.py

.ci/flake8_blacklist.txt

@@ -2,7 +2,6 @@
 .tox/
 client/node_modules/
 database/
-doc/patch.py
 doc/source/conf.py
 eggs/
 lib/galaxy/util/jstree.py

.ci/flake8_lint_include_list.txt

@@ -5,6 +5,7 @@ cron/cleanup_datasets.py
 cron/parse_builds_3_sites.py
 cron/parse_builds.py
 doc/parse_gx_xsd.py
+doc/patch.py
 lib/galaxy/actions/
 lib/galaxy/auth/
 lib/galaxy/config.py

.ci/py3_sources.txt

@@ -2,6 +2,7 @@ client/galaxy/style/source_material/circle.py
 contrib/
 cron/
 doc/parse_gx_xsd.py
+doc/patch.py
 lib/galaxy/actions/
 lib/galaxy/auth/
 lib/galaxy/config.py