progress: retry ferr.flush() and .write() on EINTR (issue5532) See the inline comment how this could mitigate the issue. I couldn't reproduce the exact problem on my Linux machine, but there are at least two people who got EINTR in progress.py, and it seems file_write() of Python 2 is fundamentally broken [1]. Let's make something in on 4.2. [1]: https://hg.python.org/cpython/file/v2.7.13/Objects/fileobject.c#l1850