Replace flake8 with ruff.

.gitignore

@@ -53,3 +53,5 @@ zope.interface-*.egg
 # This is the plaintext of the private environment needed for some CircleCI
 # operations.  It's never supposed to be checked in.
 secret-env-plain
+
+.ruff_cache

.ruff.toml

@@ -0,0 +1,12 @@
+select = [
+    # Pyflakes checks
+    "F",
+    # Prohibit tabs:
+    "W191",
+    # No trailing whitespace:
+    "W291",
+    "W293",
+    # Make sure we bind closure variables in a loop (equivalent to pylint
+    # cell-var-from-loop):
+    "B023",
+]

setup.cfg

@@ -6,6 +6,9 @@ develop = update_version develop
 bdist_egg = update_version bdist_egg
 bdist_wheel = update_version bdist_wheel
 
+# This has been replaced by ruff (see .ruff.toml), which has same checks as
+# flake8 plus many more, and is also faster. However, we're keeping this config
+# in case people still use flake8 in IDEs, etc..
 [flake8]
 # Enforce all pyflakes constraints, and also prohibit tabs for indentation.
 # Reference:

setup.py

@@ -399,12 +399,11 @@ setup(name="tahoe-lafs", # also set in __init__.py
               "gpg",
           ],
           "test": [
-              "flake8",
               # Pin a specific pyflakes so we don't have different folks
               # disagreeing on what is or is not a lint issue.  We can bump
               # this version from time to time, but we will do it
               # intentionally.
-              "pyflakes == 3.0.1",
+              "ruff==0.0.261",
               "coverage ~= 5.0",
               "mock",
               "tox ~= 3.0",

tox.ini

@@ -108,14 +108,9 @@ setenv =
 	 # entire codebase, including various pieces of supporting code.
 	 DEFAULT_FILES=src integration static misc setup.py
 commands =
-         flake8 {posargs:{env:DEFAULT_FILES}}
+         ruff check {posargs:{env:DEFAULT_FILES}}
          python misc/coding_tools/check-umids.py {posargs:{env:DEFAULT_FILES}}
          python misc/coding_tools/check-debugging.py {posargs:{env:DEFAULT_FILES}}
-         # B023: Find loop variables that aren't bound in a loop, equivalent of pylint
-         #       cell-var-from-loop.
-         # W291,W293: Trailing whitespace.
-         # ruff could probably replace flake8 and perhaps above tools as well...
-         ruff check --select=B023,W291,W293 {posargs:{env:DEFAULT_FILES}}
 
          # If towncrier.check fails, you forgot to add a towncrier news
          # fragment explaining the change in this branch.  Create one at