Fix svg writer for StringIO objects

Author: dmcdougall

lib/matplotlib/backends/backend_svg.py

@@ -1095,6 +1095,8 @@ def print_svg(self, filename, *args, **kwargs):
                     svgwriter = io.TextIOWrapper(filename, 'utf-8')
                 else:
                     svgwriter = codecs.getwriter('utf-8')(filename)
+            else:
+                svgwriter = filename
             fh_to_close = None
         else:
             raise ValueError("filename must be a path or a file-like object")