Fixes piskvorky#1869 , Mmcorpus file-like object behaviour fixed

gensim/matutils.py

@@ -1341,7 +1341,7 @@ def open_file(self, input):
                 raise
         finally:
             if not exc and isinstance(self.input, string_types):
-                exit(mgr, None, None, None)
+                type(mgr).__exit__(mgr, None, None, None)
 
     def __init__(self, input, transposed=True):
         """