typing: Convert function type annotations to Python 3 style.

Generated by com2ann (slightly patched to avoid also converting
assignment type annotations, which require Python 3.6), followed by
some manual whitespace adjustment, and two fixes for use-before-define
issues:

-    def set_zulip_client(self, zulipToJabberClient: ZulipToJabberBot) -> None:
+    def set_zulip_client(self, zulipToJabberClient: 'ZulipToJabberBot') -> None:

-def init_from_options(options: Any, client: Optional[str] = None) -> Client:
+def init_from_options(options: Any, client: Optional[str] = None) -> 'Client':

Signed-off-by: Anders Kaseorg <anders@zulipchat.com>

zulip/integrations/codebase/zulip_codebase_mirror

@@ -50,8 +50,7 @@ while len(json_implementations):
     except ImportError:
         continue
 
-def make_api_call(path):
-    # type: (str) -> Optional[List[Dict[str, Any]]]
+def make_api_call(path: str) -> Optional[List[Dict[str, Any]]]:
     response = requests.get("https://api3.codebasehq.com/%s" % (path,),
                             auth=(config.CODEBASE_API_USERNAME, config.CODEBASE_API_KEY),
                             params={'raw': 'True'},
@@ -71,12 +70,10 @@ def make_api_call(path):
         logging.warn("Found non-success response status code: %s %s" % (response.status_code, response.text))
         return None
 
-def make_url(path):
-    # type: (str) -> str
+def make_url(path: str) -> str:
     return "%s/%s" % (config.CODEBASE_ROOT_URL, path)
 
-def handle_event(event):
-    # type: (Dict[str, Any]) -> None
+def handle_event(event: Dict[str, Any]) -> None:
     event = event['event']
     event_type = event['type']
     actor_name = event['actor_name']
@@ -240,12 +237,10 @@ def handle_event(event):
 
 
 # the main run loop for this mirror script
-def run_mirror():
-    # type: () -> None
+def run_mirror() -> None:
     # we should have the right (write) permissions on the resume file, as seen
     # in check_permissions, but it may still be empty or corrupted
-    def default_since():
-        # type: () -> datetime
+    def default_since() -> datetime:
         return datetime.now(tz=pytz.utc) - timedelta(hours=config.CODEBASE_INITIAL_HISTORY_HOURS)
 
     try:
@@ -282,8 +277,7 @@ def run_mirror():
         logging.info("Shutting down Codebase mirror")
 
 # void function that checks the permissions of the files this script needs.
-def check_permissions():
-    # type: () -> None
+def check_permissions() -> None:
     # check that the log file can be written
     if config.LOG_FILE:
         try: