openpyxl leaks file handle in pypy

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$ python test.py
number of open file handles: 0
number of open file handles: 2
[popenfile(path='/Users/github/pyexcel-xlsx/test.xlsx', fd=5), popenfile(path='/Users/github/pyexcel-xlsx/test.xlsx', fd=6)]
Traceback (most recent call last):
  File "test.py", line 14, in <module>
    assert len(open_files_l1) == len(open_files_l2)
AssertionError
$ python
Python 2.7.13 (1aa2d8e03cdf, Mar 31 2017, 10:20:53)
[PyPy 5.7.1 with GCC 4.2.1 Compatible Apple LLVM 5.1 (clang-503.0.40)] on darwin
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reference: #14

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The bug is reported in openpyxl

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but the openpyxl won't fix.