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/zephyr/check-mirroring

@@ -82,8 +82,7 @@ else:
         ("tabbott-nagios-test", "a"),
     ]
 
-def print_status_and_exit(status):
-    # type: (int) -> None
+def print_status_and_exit(status: int) -> None:
 
     # The output of this script is used by Nagios. Various outputs,
     # e.g. true success and punting due to a SERVNAK, result in a
@@ -92,8 +91,7 @@ def print_status_and_exit(status):
     print(status)
     sys.exit(status)
 
-def send_zulip(message):
-    # type: (Dict[str, str]) -> None
+def send_zulip(message: Dict[str, str]) -> None:
     result = zulip_client.send_message(message)
     if result["result"] != "success":
         logger.error("Error sending zulip, args were:")
@@ -102,8 +100,7 @@ def send_zulip(message):
         print_status_and_exit(1)
 
 # Returns True if and only if we "Detected server failure" sending the zephyr.
-def send_zephyr(zwrite_args, content):
-    # type: (List[str], str) -> bool
+def send_zephyr(zwrite_args: List[str], content: str) -> bool:
     p = subprocess.Popen(zwrite_args, stdin=subprocess.PIPE,
                          stdout=subprocess.PIPE, stderr=subprocess.PIPE)
     stdout, stderr = p.communicate(input=content.encode("utf-8"))
@@ -167,16 +164,14 @@ if not actually_subscribed:
 # Prepare keys
 zhkeys = {}  # type: Dict[str, Tuple[str, str]]
 hzkeys = {}  # type: Dict[str, Tuple[str, str]]
-def gen_key(key_dict):
-    # type: (Dict[str, Any]) -> str
+def gen_key(key_dict: Dict[str, Any]) -> str:
     bits = str(random.getrandbits(32))
     while bits in key_dict:
         # Avoid the unlikely event that we get the same bits twice
         bits = str(random.getrandbits(32))
     return bits
 
-def gen_keys(key_dict):
-    # type: (Dict[str, Tuple[str, str]]) -> None
+def gen_keys(key_dict: Dict[str, Tuple[str, str]]) -> None:
     for (stream, test) in test_streams:
         key_dict[gen_key(key_dict)] = (stream, test)
 
@@ -188,8 +183,7 @@ notices = []
 # We check for new zephyrs multiple times, to avoid filling the zephyr
 # receive queue with 30+ messages, which might result in messages
 # being dropped.
-def receive_zephyrs():
-    # type: () -> None
+def receive_zephyrs() -> None:
     while True:
         try:
             notice = zephyr.receive(block=False)
@@ -271,8 +265,7 @@ receive_zephyrs()
 logger.info("Finished receiving Zephyr messages!")
 
 all_keys = set(list(zhkeys.keys()) + list(hzkeys.keys()))
-def process_keys(content_list):
-    # type: (List[str]) -> Tuple[Dict[str, int], Set[str], Set[str], bool, bool]
+def process_keys(content_list: List[str]) -> Tuple[Dict[str, int], Set[str], Set[str], bool, bool]:
 
     # Start by filtering out any keys that might have come from
     # concurrent check-mirroring processes