Kill doctest in dulwich.file. This breaks the epytext parser.

dulwich/file.py

@@ -71,22 +71,7 @@ def GitFile(filename, mode='rb', bufsize=-1):
     Only read-only and write-only (binary) modes are supported; r+, w+, and a
     are not.  To read and write from the same file, you can take advantage of
     the fact that opening a file for write does not actually open the file you
-    request:
-
-    >>> write_file = GitFile('filename', 'wb')
-    >>> read_file = GitFile('filename', 'rb')
-    >>> read_file.readlines()
-    ['contents\n', 'of\n', 'the\n', 'file\n']
-    >>> write_file.write('foo')
-    >>> read_file.close()
-    >>> write_file.close()
-    >>> new_file = GitFile('filename', 'rb')
-    'foo'
-    >>> new_file.close()
-    >>> other_file = GitFile('filename', 'wb')
-    Traceback (most recent call last):
-        ...
-    OSError: [Errno 17] File exists: 'filename.lock'
+    request.
     """
     if 'a' in mode:
         raise IOError('append mode not supported for Git files')