fixes in order to support NetworkManager

I wanted to generate stubs using this tool for NetworkManager (NM).

What I found was failures for two reasons:

1. Cannot generate due to invalid identifiers (80211Flags).
1. Some enums with no entries.

I fixed this by:

1. Quoting those identifiers. My belief is that this will keep mypy
   working but fixing the python level issues.
1. Printing `pass` after each enum with empty entries.

tools/generate.py

@@ -313,7 +313,11 @@ def _type_to_python(
                 return f"typing.Callable[[{', '.join(args)}], {return_type}]"
         else:
             namespace = interface.get_namespace()
-            name = interface.get_name()
+            raw_name = interface.get_name()
+            if raw_name[0].isdigit():
+                name = f'"{raw_name}"'
+            else:
+                name = raw_name
 
             if namespace == "GObject" and name == "Value":
                 return "typing.Any"
@@ -885,6 +889,7 @@ def _gi_build_stub(
             base = "GObject.GEnum"
 
         ret += f"class {name}({base}):\n"
+        any_variants = False
         for key in sorted(vars(obj)):
             if key.startswith("__") or key[0].isdigit():
                 continue
@@ -907,6 +912,9 @@ def _gi_build_stub(
                 ret += f"    {key} = {value}\n"
             else:
                 ret += f"    {key} = ... # FIXME Enum\n"
+            any_variants = True
+        if not any_variants:
+            ret += "    pass\n"
         ret += "\n"
 
     return ret