skip Emacs/vim backup files (#331)

* skip Emacs/vim backup files

* requested change

Author: smontanaro

pyflakes/api.py

@@ -117,6 +117,10 @@ def isPythonFile(filename):
     if filename.endswith('.py'):
         return True
 
+    # Avoid obvious Emacs backup files
+    if filename.endswith("~"):
+        return False
+
     max_bytes = 128
 
     try:

pyflakes/test/test_api.py

@@ -180,6 +180,7 @@ def test_recurses(self):
         """
         os.mkdir(os.path.join(self.tempdir, 'foo'))
         apath = self.makeEmptyFile('foo', 'a.py')
+        self.makeEmptyFile('foo', 'a.py~')
         os.mkdir(os.path.join(self.tempdir, 'bar'))
         bpath = self.makeEmptyFile('bar', 'b.py')
         cpath = self.makeEmptyFile('c.py')