visualize_pf.py not working

[gsell]

As reported by Finn O'Shea:

I couldn't get visualize_pf.py to work. The first bug I found is on line 384:
print("Show generation " + generation)
that should read str(generation) otherwise a TypeError is raised. Even after fixing that bug, there was at least one more.

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Migrated from GitLab
GitLab ID: 94
Source: https://gitlab.psi.ch/OPAL/pyOPALTools/-/issues/94
Original state: opened
Original author: snuverink_j