[#65] Workaround for non-ascii filename uploads

Quite silly, but until the problem is fixed on the server side,
it seems like this workaround is the best solution there is.

mwclient/client.py

@@ -511,6 +511,21 @@ class Site(object):
         postdata = predata
         files = None
         if file is not None:
+
+            # Workaround for https://github.com/mwclient/mwclient/issues/65
+            # ----------------------------------------------------------------
+            # Since the filename in Content-Disposition is not used as the
+            # destination filename, we can pass in some ascii-only dummy name
+            # to make sure the server accepts it.
+            fname = 'upload'
+            name = getattr(file, 'name', None)
+            if name and name[0] != '<' and name[-1] != '>' and name.find('.') != -1:
+                ext = name[name.rfind('.') + 1:]
+                fname = 'upload.{}'.format(ext)
+            file = (fname, file)
+            # End of workaround
+            # ----------------------------------------------------------------
+
             files = {'file': file}
 
         wait_token = self.wait_token()