.flake8: limit to rules not covered by ruff

Our current flake8 config overlaps our ruff config.  Since we want to
slowly move away from flake8, enable only the pycodestyle rules that we
don't get from ruff.

Once ruff implements the outstanding rules, we can drop flake8.

.flake8

@@ -1,14 +1,8 @@
 [flake8]
-ignore=
-    # line break after binary operator
-    W504
-builtins =
-    # inotify.py get pasted together with other files
-    Inotify,
-    IN_CREATE, IN_MOVED_TO,
-    IN_MOVED_FROM, IN_MOVE_SELF,
-    IN_DELETE, IN_DELETE_SELF,
-    IN_CLOSE_WRITE,
-    IN_IGNORED,
-
-max-line-length = 200
+# Use flake8 only to cover rules not yet supported (or enabled by
+# default) with ruff.  See https://github.com/astral-sh/ruff/issues/2402
+# and https://github.com/astral-sh/ruff/releases/tag/v0.0.269
+select=
+  E1
+  E2
+  E3

test/static-code

@@ -3,6 +3,7 @@
 
 set -eu
 
+# requires: .flake8
 # requires: pyproject.toml
 # requires: containers/flatpak/test/ruff.toml
 # requires: pkg/ruff.toml