Bump Python to >= 3.7

.github/workflows/unit_tests.yml

@@ -7,7 +7,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ['3.6', '3.7', '3.8', '3.9', '3.10']
+        python-version: ['3.7', '3.8', '3.9', '3.10']
         sphinx-version:
           - '4.0.3'
           - '4.1.2'
@@ -19,10 +19,6 @@ jobs:
           - '5.3.0'
           - git+https://github.com/sphinx-doc/sphinx.git@master
         exclude:
-          # Since sphinx 7e68154e49fbb260f7ffee9791bfafdb7fd2e119 python 3.6
-          # support is removed. Breathe will probably also drop 3.6 soon.
-          - python-version: '3.6'
-            sphinx-version: git+https://github.com/sphinx-doc/sphinx.git@master
           # avoid bug in following configurations
           # sphinx/util/typing.py:37: in <module>
           #     from types import Union as types_Union

setup.py

@@ -19,8 +19,8 @@
 
 requires = ["Sphinx>=4.0,<6,!=5.0.0", "docutils>=0.12"]
 
-if sys.version_info < (3, 6):
-    print("ERROR: Sphinx requires at least Python 3.6 to run.")
+if sys.version_info < (3, 7):
+    print("ERROR: Sphinx requires at least Python 3.7 to run.")
     sys.exit(1)