Compatibility with Python 3.7

[jnogol]

Prerequisites

• Put an X between the brackets on this line if you have done all of the following:
  • Checked that your issue isn't already filled: https://github.com/issues?utf8=✓&q=is%3Aissue+user%3Aidealista
  • Checked that there is not already provided the described functionality

Description

Check if Prom2teams is already compatible with Python 3.7 and, if it doesn't, make it so.

[dortegau]

As Python 3.8 is the current stable version, should be checked with that version :)

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[blalop]

Closing as this is already supported