color: handle more Windows console errors

If your application is being built as a non-console application,
stdout is not a valid handle and raises an exception:

pywintypes.error: (6, 'DuplicateHandle', 'The handle is invalid.')

Alternatively, non-console applications launched outside of a
console will return None from GetStdHandle instead of raising an
exception.

hgext/color.py

@@ -254,8 +254,10 b' try:'
         'inverse': win32c.COMMON_LVB_REVERSE_VIDEO, # double-byte charsets only
     }
 
+    try:
     stdout = win32c.GetStdHandle(win32c.STD_OUTPUT_HANDLE)
-    try:
+        if stdout is None:
+            raise ImportError()
         origattr = stdout.GetConsoleScreenBufferInfo()['Attributes']
     except pywintypes.error:
         # stdout may be defined but not support