Clean up some remaining Python version references

README.asciidoc

@@ -98,7 +98,7 @@ websites and using it for transmission of sensitive data._
 
 On older Python versions (3.7/3.8), the following backports are also required:
 
-* https://importlib-resources.readthedocs.io/[importlib_resources] (Python 3.8 or older)
+* https://importlib-resources.readthedocs.io/[importlib_resources]
 
 The following libraries are optional:
 
@@ -108,8 +108,8 @@ The following libraries are optional:
   QtWebEngine backend.
 * On Windows, https://pypi.python.org/pypi/colorama/[colorama] for colored log
   output.
-* https://importlib-metadata.readthedocs.io/[importlib_resources] on Python 3.7
-  or older, to improve QtWebEngine version detection when PyQtWebEngine is
+* https://importlib-metadata.readthedocs.io/[importlib_metadata] on Python 3.7,
+  to improve QtWebEngine version detection when PyQtWebEngine is
   installed via pip (thus, this dependency usually isn't relevant for
   packagers).
 * https://asciidoc.org/[asciidoc] to generate the documentation for the `:help`

doc/contributing.asciidoc

@@ -546,9 +546,6 @@ Setting up a Windows Development Environment
 
 * Install https://www.python.org/downloads/release/python-3911/[Python 3.9].
 * Install PyQt via `pip install PyQt5`.
-* Create a file at `C:\Windows\system32\python3.bat` with the following content (adjust the path as necessary):
-  `@C:\Python36\python %*`.
-  This will make the Python 3.9 interpreter available as `python3`, which is used by various development scripts.
 * Install git from the https://git-scm.com/download/win[git-scm downloads page].
   Try not to enable `core.autocrlf`, since that will cause `flake8` to complain a lot. Use an editor that can deal with plain line feeds instead.
 * Clone your favourite qutebrowser repository.

scripts/dev/check_coverage.py

@@ -333,7 +333,7 @@ def main_check():
         subprocess.run([sys.executable, '-m', 'coverage', 'report',
                         '--show-missing', '--include', filters], check=True)
         print()
-        print("To debug this, run 'tox -e py36-pyqt515-cov' "
+        print("To debug this, run 'tox -e py39-pyqt515-cov' "
               "(replace Python/Qt versions based on your system) locally and check "
               "htmlcov/index.html")
         print("or check https://codecov.io/github/qutebrowser/qutebrowser")
@@ -353,7 +353,7 @@ def main_check_all():
     tests.
 
     This runs pytest with the used executable, so check_coverage.py should be
-    called with something like ./.tox/py36/bin/python.
+    called with something like ./.tox/py39/bin/python.
     """
     for test_file, src_file in PERFECT_FILES:
         if test_file is None:

tests/unit/utils/test_utils.py

@@ -931,7 +931,7 @@ def test_parse_duration_hypothesis(duration):
 
 @pytest.mark.parametrize('mimetype, extension', [
     ('application/pdf', '.pdf'),  # handled by Python
-    ('text/plain', '.txt'),  # wrong in Python 3.6, overridden
+    ('text/plain', '.txt'),  # was wrong in Python 3.6, handled now
     ('application/manifest+json', '.webmanifest'),  # newer
     ('text/xul', '.xul'),  # strict=False
     ('doesnot/exist', None),