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.

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: