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_botserver/setup.py

@@ -59,8 +59,7 @@ except ImportError:
     from importlib import import_module
 
     # Manual dependency check
-    def check_dependency_manually(module_name, version=None):
-        # type: (str, Optional[str]) -> None
+    def check_dependency_manually(module_name: str, version: Optional[str] = None) -> None:
         try:
             module = import_module(module_name)  # type: Any
             if version is not None: