This failed once in CI for the python 3.5 test, but not for the other two version, with a ConnectionRefusedError on an ftp test. This seems unrelated to the changes introduced by the PR. I've restarted that test to see if it passes.

looks like our pytest marks are broken by this PR on 3.5 but not on other versions(!)

This now passes in CI: on my laptop, with no pytest installed, the most recent valid pytest was install (4.6.6). In CI, pytest 4.1.0 is pre-installed. This was also valid according to the requirements I added, but didn't work. I've updated the requirements to >=4.6 and this now passes in CI.

I'm seeing a bunch of

--- Logging error ---
Traceback (most recent call last):
  File "/opt/python/3.5.6/lib/python3.5/logging/__init__.py", line 988, in emit
    stream.write(msg)
  File "/home/travis/virtualenv/python3.5.6/lib/python3.5/site-packages/_pytest/capture.py", line 441, in write
    self.buffer.write(obj)
ValueError: I/O operation on closed file
Call stack:
  File "/home/travis/build/Parsl/parsl/parsl/dataflow/dflow.py", line 855, in atexit_cleanup
    self.cleanup()
  File "/home/travis/build/Parsl/parsl/parsl/dataflow/dflow.py", line 882, in cleanup
    logger.info("DFK cleanup initiated")
Message: 'DFK cleanup initiated'
Arguments: ()

at the end of the --config local test run - although this does not cause pytest to fail with an exit code.

It looks related to this pytest issue to do with module imports setting up logging: pytest-dev/pytest#5502

These I/O operation on closed file errors also happen on my dev laptop.

It looks like the error messages that I reported were caused by test cases calling parsl.set_stream_logger() when they were imported, resulting in log configuration to stderr/stdout that this newer version of pytest does not like.

Those calls shouldn't have been made anyway, so I've removed them / moved to __main__ blocks in 4838b8a and the error messages no longer happen.

@yadudoc please can you look at this again?