Fix exception on mingw built Python 2

msvc9compiler doesn't like being imported on mingw built Python. It
throws DistutilsPlatformError, so catch it.

Fixes #1118

setuptools/monkey.py

@@ -4,7 +4,6 @@ Monkey patching of distutils.
 
 import sys
 import distutils.filelist
-from distutils.util import get_platform
 import platform
 import types
 import functools
@@ -153,13 +152,13 @@ def patch_for_msvc_specialized_compiler():
     Patch functions in distutils to use standalone Microsoft Visual C++
     compilers.
     """
-    if not get_platform().startswith('win'):
-        # Compilers only availables on Microsoft Windows
-        return
-
     # import late to avoid circular imports on Python < 3.5
     msvc = import_module('setuptools.msvc')
 
+    if platform.system() != 'Windows':
+        # Compilers only availables on Microsoft Windows
+        return
+
     def patch_params(mod_name, func_name):
         """
         Prepare the parameters for patch_func to patch indicated function.

setuptools/msvc.py

@@ -47,7 +47,7 @@ else:
 
 try:
     from distutils.msvc9compiler import Reg
-except ImportError:
+except (ImportError, distutils.errors.DistutilsPlatformError):
     pass