Don't bonk if .netrc isn't readable.

It's possible in some shared hosting environments that the .netrc file isn't readable by the user for the calling process. In that circumstance, just forgo the netrc authentication.

requests/utils.py

@@ -50,7 +50,9 @@ def get_netrc_auth(url):
             # Return with login / password
             login_i = (0 if _netrc[0] else 1)
             return (_netrc[login_i], _netrc[2])
-    except NetrcParseError:
+    except NetrcParseError, IOError:
+        # If there was a parsing error or a permissions issue reading the file,
+        # we'll just skip netrc auth
         pass