Fix a number of flake8 errors

Broadly three things here:

* disable W504 which seems a bit whacko
* remove a bunch of `as e` expressions from exception handlers that don't use
  them
* use `r""` for strings which include backslashes

Also, we don't use pep8 any more, so we can get rid of the duplicate config
there.

changelog.d/4082.misc

@@ -0,0 +1 @@
+Clean up some bits of code which were flagged by the linter

scripts-dev/tail-synapse.py

@@ -48,7 +48,7 @@ def main():
                 row.name: row.position
                 for row in replicate(server, {"streams": "-1"})["streams"].rows
             }
-        except requests.exceptions.ConnectionError as e:
+        except requests.exceptions.ConnectionError:
             time.sleep(0.1)
 
     while True:

scripts/synapse_port_db

@@ -501,7 +501,8 @@ class Porter(object):
 
             try:
                 yield self.postgres_store.runInteraction("alter_table", alter_table)
-            except Exception as e:
+            except Exception:
+                # On Error Resume Next
                 pass
 
             yield self.postgres_store.runInteraction(

setup.cfg

@@ -14,17 +14,16 @@ ignore =
     pylint.cfg
     tox.ini
 
-[pep8]
-max-line-length = 90
-#  W503 requires that binary operators be at the end, not start, of lines. Erik
-#  doesn't like it.  E203 is contrary to PEP8.  E731 is silly.
-ignore = W503,E203,E731
-
 [flake8]
-# note that flake8 inherits the "ignore" settings from "pep8" (because it uses
-# pep8 to do those checks), but not the "max-line-length" setting
 max-line-length = 90
-ignore=W503,E203,E731
+
+# see https://pycodestyle.readthedocs.io/en/latest/intro.html#error-codes
+# for error codes. The ones we ignore are:
+#  W503: line break before binary operator
+#  W504: line break after binary operator
+#  E203: whitespace before ':' (which is contrary to pep8?)
+#  E731: do not assign a lambda expression, use a def
+ignore=W503,W504,E203,E731
 
 [isort]
 line_length = 89

synapse/config/repository.py

@@ -178,7 +178,7 @@ class ContentRepositoryConfig(Config):
     def default_config(self, **kwargs):
         media_store = self.default_path("media_store")
         uploads_path = self.default_path("uploads")
-        return """
+        return r"""
         # Directory where uploaded images and attachments are stored.
         media_store_path: "%(media_store)s"
 

synapse/crypto/keyclient.py

@@ -55,7 +55,7 @@ def fetch_server_key(server_name, tls_client_options_factory, path=KEY_API_V1):
                 raise IOError("Cannot get key for %r" % server_name)
         except (ConnectError, DomainError) as e:
             logger.warn("Error getting key for %r: %s", server_name, e)
-        except Exception as e:
+        except Exception:
             logger.exception("Error getting key for %r", server_name)
     raise IOError("Cannot get key for %r" % server_name)
 

synapse/federation/federation_server.py

@@ -800,7 +800,7 @@ class FederationHandlerRegistry(object):
             yield handler(origin, content)
         except SynapseError as e:
             logger.info("Failed to handle edu %r: %r", edu_type, e)
-        except Exception as e:
+        except Exception:
             logger.exception("Failed to handle edu %r", edu_type)
 
     def on_query(self, query_type, args):

synapse/rest/client/v2_alpha/auth.py

@@ -99,7 +99,7 @@ class AuthRestServlet(RestServlet):
     cannot be handled in the normal flow (with requests to the same endpoint).
     Current use is for web fallback auth.
     """
-    PATTERNS = client_v2_patterns("/auth/(?P<stagetype>[\w\.]*)/fallback/web")
+    PATTERNS = client_v2_patterns(r"/auth/(?P<stagetype>[\w\.]*)/fallback/web")
 
     def __init__(self, hs):
         super(AuthRestServlet, self).__init__()

synapse/rest/media/v1/preview_url_resource.py

@@ -674,7 +674,7 @@ def summarize_paragraphs(text_nodes, min_size=200, max_size=500):
         # This splits the paragraph into words, but keeping the
         # (preceeding) whitespace intact so we can easily concat
         # words back together.
-        for match in re.finditer("\s*\S+", description):
+        for match in re.finditer(r"\s*\S+", description):
             word = match.group()
 
             # Keep adding words while the total length is less than

synapse/storage/registration.py

@@ -567,7 +567,7 @@ class RegistrationStore(RegistrationWorkerStore,
         def _find_next_generated_user_id(txn):
             txn.execute("SELECT name FROM users")
 
-            regex = re.compile("^@(\d+):")
+            regex = re.compile(r"^@(\d+):")
 
             found = set()
 

tests/config/test_generate.py

@@ -67,6 +67,6 @@ class ConfigGenerationTestCase(unittest.TestCase):
         with open(log_config_file) as f:
             config = f.read()
             # find the 'filename' line
-            matches = re.findall("^\s*filename:\s*(.*)$", config, re.M)
+            matches = re.findall(r"^\s*filename:\s*(.*)$", config, re.M)
             self.assertEqual(1, len(matches))
             self.assertEqual(matches[0], expected)

tests/events/test_utils.py

@@ -156,7 +156,7 @@ class SerializeEventTestCase(unittest.TestCase):
                     room_id="!foo:bar",
                     content={"key.with.dots": {}},
                 ),
-                ["content.key\.with\.dots"],
+                [r"content.key\.with\.dots"],
             ),
             {"content": {"key.with.dots": {}}},
         )
@@ -172,7 +172,7 @@ class SerializeEventTestCase(unittest.TestCase):
                         "nested.dot.key": {"leaf.key": 42, "not_me_either": 1},
                     },
                 ),
-                ["content.nested\.dot\.key.leaf\.key"],
+                [r"content.nested\.dot\.key.leaf\.key"],
             ),
             {"content": {"nested.dot.key": {"leaf.key": 42}}},
         )