syntax checker fails when python file does not exist yet

[Curtis Hovey]

The a new python file is is checked, pep8 dies.

Traceback (most recent call last):
  File "/home/curtis/.local/share/gedit/plugins/gdp/format.py", line 321, in check_style
    self._check_style(document)
  File "/home/curtis/.local/share/gedit/plugins/gdp/format.py", line 313, in _check_style
    checker.check()
  File "/usr/lib/pymodules/python2.7/pocketlint/formatcheck.py", line 293, in check
    checker.check()
  File "/usr/lib/pymodules/python2.7/pocketlint/formatcheck.py", line 502, in check
    self.check_pep8()
  File "/usr/lib/pymodules/python2.7/pocketlint/formatcheck.py", line 535, in check_pep8
    pep8.Checker(self.file_path).check_all()
  File "/usr/lib/pymodules/python2.7/pocketlint/contrib/pep8.py", line 827, in __init__
    self.lines = readlines(filename)
  File "/usr/lib/pymodules/python2.7/pocketlint/contrib/pep8.py", line 723, in readlines
    return open(filename).readlines()
IOError: [Errno 2] No such file or directory: '/home/curtis/Work/test.py'