Need to add configparser to list of requirements

[hickey]

Since Python2 is EOL I am building markupserve in the python:2-alpine container. Once the requirements from requirements.txt are installed, I attempt to execute markupserve and end up with another dependency that was not installed.

/tmp/markupserve # python2 markupserve.py -h
Traceback (most recent call last):
  File "markupserve.py", line 11, in <module>
    import configparser
ImportError: No module named configparser

Once installed with pip, markupserve starts up as expected.