remove explicit python3.9 reference due to pylint

3.8 will be used if available

docs/development.md

@@ -26,11 +26,9 @@ $ pyenv/bin/python -c 'import aqt; aqt.run()'
 
 From Anki 2.1.36 onwards:
 
-- Make sure your pip version is 20 or later (pip install --upgrade pip).
-- Then:
-
 ```
 $ python -m venv pyenv
+$ pyenv/bin/pip install --upgrade pip
 $ pyenv/bin/pip install aqt
 $ pyenv/bin/python -c 'import aqt; aqt.run()'
 ```
@@ -58,6 +56,8 @@ From inside the source folder:
 bazel test //...
 ```
 
+Pylint will currently fail if you're using Python 3.9.
+
 ## Fixing formatting
 
 If the format tests fail, most can be fixed by running `format`
@@ -84,8 +84,8 @@ bazel build -c opt //pylib/anki:wheel
 bazel build -c opt //qt/aqt:wheel
 ```
 
-The generated wheel paths will be printed as the build completes. To install
-them, see earlier in this document.
+The generated wheel paths will be printed as the build completes. You can install
+them with pip.
 
 ## Audio
 

docs/linux.md

@@ -20,13 +20,14 @@ If you're on a modern distribution, you may be able to install Python from the r
 $  sudo apt install python3.8
 ```
 
-If python3.8 is not available in your distro, you can download it from python.org.
+If Python 3.8 is not available in your distro, you can download it from python.org,
+compile it, and install in in /usr/local.
 
-Notes:
+If your system only has Python 3.9, you should be able to build Anki with it,
+but the pylint tests will currently fail, as pylint does not yet support Python 3.9.
 
-- The build scripts expect to find 'python3.8' on your path, so Python 3.7 or 3.9 will
-  not work.
-- An active Python venv is not required, and may cause problems.
+Anki's build system will not place packages in system locations, so you do not
+need to build with an active Python virtual environmental.
 
 **Install Bazelisk**:
 

docs/mac.md

@@ -22,6 +22,8 @@ $ brew install rsync bazelisk
 Install Python 3.8 from <https://python.org>. You may be able to use
 the Homebrew version instead, but this is untested.
 
+Python 3.9 is not currently recommended, as pylint does not support it yet.
+
 You do not need to set up a Python venv prior to building Anki.
 
 When you run "python" in a shell, if it shows Python 2.x, you may get a
@@ -32,6 +34,9 @@ pointing python to python3.8:
 $ ln -sf /usr/local/bin/{python3.8,python}
 ```
 
+This linking will not work if you're using the system Python from Big Sur,
+which is one of the reasons why we recommend using Python from python.org.
+
 ## Running Anki during development
 
 From the top level of Anki's source folder:
@@ -42,7 +47,7 @@ From the top level of Anki's source folder:
 
 This will build Anki and run it in place.
 
-The first build will take while, as it downloads and builds a bunch of
+The first build will take a while, as it downloads and builds a bunch of
 dependencies. When the build is complete, Anki will automatically start.
 
 To play audio, use Homebrew to install mpv. At the time of writing, recording is

docs/windows.md

@@ -24,6 +24,8 @@ Python to be installed in that location.
 
 When the install is done, click on the "remove the path limit" button.
 
+Python 3.9 is not currently recommended, as pylint does not support it yet.
+
 **MSYS**:
 
 Install [msys2](https://www.msys2.org/) into the default folder location.

python.bzl

@@ -1,6 +1,12 @@
 def _impl(rctx):
     # locate python on path, and export it
-    names = ["python3.9", "python3.8", "python3", "python.exe"]
+    names = [
+        # prefer 3.8 over 3.9, as pylint currently fails on 3.9
+        # (due to issues like https://github.com/PyCQA/pylint/pull/3890)
+        "python3.8",
+        "python3",
+        "python.exe",
+    ]
     path = None
     for name in names:
         path = rctx.which(name)