svgwriter not assigned in FigureCanvasSVG.print_svg for StringIO filename #1373

#!/usr/bin/python2

from io import StringIO

from matplotlib.backends.backend_svg import FigureCanvasSVG
from matplotlib.figure import Figure

output = StringIO()
fig = Figure()
canvas = FigureCanvasSVG(fig)
canvas.print_svg(output)

Traceback (most recent call last):
  File "./print_svg.py", line 11, in <module>
    canvas.print_svg(output)
  File "/usr/lib64/python2.7/site-packages/matplotlib/backends/backend_svg.py", line 1101, in print_svg
    return self._print_svg(filename, svgwriter, fh_to_close, **kwargs)
UnboundLocalError: local variable 'svgwriter' referenced before assignment