Trac #34425: configure vscode pycodestyle linter

The goal of this ticket is to configure the vscode pycodestyle linter to
check against Sage's minimal style conventions:
    * E111: indentation is not a multiple of four
    * E306: expected 1 blank line before a nested definition, found 0
    * E401: multiple imports on one line
    * E701: multiple statements on one line (colon)
    * E702: multiple statements on one line (semicolon)
    * E703: statement ends with a semicolon
    * E711: comparison to None should be ‘if cond is None:’
    * E712: comparison to True should be ‘if cond is True:’ or ‘if
cond:’
    * E713: test for membership should be 'not in'
    * E721: do not compare types, use isinstance()
    * E722: do not use bare except, specify exception instead
    * W605: invalid escape sequence ‘x’

See https://pycodestyle.pycqa.org/en/latest/intro.html#error-codes

URL: https://trac.sagemath.org/34425
Reported by: gh-DavidAyotte
Ticket author(s): David Ayotte
Reviewer(s): Matthias Koeppe

.vscode/settings.json

@@ -1,4 +1,6 @@
 {
+    // This settings file is not ignored by git. It should be kept in sync with
+    // the trac repo.
     "python.defaultInterpreterPath": "./venv/bin/python3",
     "files.exclude": {
         "**/__pycache__": true,
@@ -23,6 +25,9 @@
     "python.testing.unittestEnabled": false,
     "python.linting.pycodestyleEnabled": true,
     "python.linting.enabled": true,
+    // The following pycodestyle arguments are the same as the pycodestyle-minimal
+    // tox environnment, see the file SAGE_ROOT/src/tox.ini
+    "python.linting.pycodestyleArgs": ["--select=E111,E306,E401,E701,E702,E703,W605,E711,E712,E713,E721,E722"],
     "cSpell.words": [
         "furo",
         "Conda",

src/doc/en/developer/tools.rst

@@ -196,7 +196,12 @@ or a few related issues::
 
 - Manual: Run ``pycodestyle path/to/the/file.py``.
 
-- VS Code: Activate by adding the setting ``"python.linting.pycodestyleEnabled": true``, see `official VS Code documentation <https://code.visualstudio.com/docs/python/linting>`__ for details.
+- VS Code: The minimal version of pycodestyle is activated by default in
+  ``SAGE_ROOT/.vscode/settings.json`` (the corresponding setting is
+  ``"python.linting.pycodestyleEnabled": true``). Note that the
+  ``settings.json`` file is not ignored by git so be aware to keep it in sync
+  with the trac repo. For further details, see the
+  `official VS Code documentation <https://code.visualstudio.com/docs/python/linting>`__.
 
 *Configuration:* ``[pycodestyle]`` block in ``SAGE_ROOT/src/tox.ini``
 

src/tox.ini

@@ -90,6 +90,8 @@ deps = pycodestyle
 commands = pycodestyle {posargs:{toxinidir}/sage/}
 
 [testenv:pycodestyle-minimal]
+## Note that the the pycodestyle linter provided by vscode checks against the
+## same minimal conventions as defined below, see the file SAGE_ROOT/.vscode/settings.json.
 description =
     check against Sage's minimal style conventions
     # Check for the following issues: