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_bots/zulip_bots/test_lib.py

@@ -53,13 +53,11 @@ class StubBotHandler:
     def update_message(self, message: Dict[str, Any]) -> None:
         self.message_server.update(message)
 
-    def upload_file_from_path(self, file_path):
-        # type: (str) -> Dict[str, Any]
+    def upload_file_from_path(self, file_path: str) -> Dict[str, Any]:
         with open(file_path, 'rb') as file:
             return self.message_server.upload_file(file)
 
-    def upload_file(self, file):
-        # type: (IO[Any]) -> Dict[str, Any]
+    def upload_file(self, file: IO[Any]) -> Dict[str, Any]:
         return self.message_server.upload_file(file)
 
     class BotQuitException(Exception):
@@ -132,8 +130,7 @@ class BotTestCase(unittest.TestCase):
 
         return bot, bot_handler
 
-    def get_response(self, message):
-        # type: (Dict[str, Any]) -> Dict[str, Any]
+    def get_response(self, message: Dict[str, Any]) -> Dict[str, Any]:
         bot, bot_handler = self._get_handlers()
         bot_handler.reset_transcript()
         bot.handle_message(message, bot_handler)