Issue 467; fix Nameerror with copy function. Added issue to tests..

moviepy/video/fx/blink.py

@@ -1,10 +1,12 @@
+import copy
+
 def blink(clip, d_on, d_off):
     """
     Makes the clip blink. At each blink it will be displayed ``d_on``
     seconds and disappear ``d_off`` seconds. Will only work in
     composite clips.
     """
-    newclip = copy(clip)
+    newclip = copy.copy(clip)
     if newclip.mask is None:
         newclip = newclip.with_mask()
     D = d_on + d_off

tests/test_issues.py

@@ -59,5 +59,12 @@ def test_issue_417():
     final = CompositeVideoClip([myclip], size=(1280, 720))
     #final.set_duration(7).write_videofile("test.mp4", fps=30)
 
+def test_issue_467():
+    cad = 'media/python_logo.png'
+    clip = ImageClip(cad)
+
+    #caused an error, NameError: global name 'copy' is not defined
+    clip = clip.fx(vfx.blink, d_on=1, d_off=1)
+
 if __name__ == '__main__':
    pytest.main()