Is the dependency "common" really needed?

Problem to solve

Currently, "common" is listed as a dependency for carputils, but I don't think it is actually required.

Further details

The only occurence to the dependency I could find is in the file carputils/model/generate_carpentry.py, and I actually don't think it is supposed to be importing the "common" Python package, because there is no function readIMPs in it.

def limpet_read_imps(limpetdir):
    """
    Append LIMPET path ahead of other PATH includes.
    Matters across different CARP versions.
    """
    sys.path.insert(0, limpetdir)
    #print(sys.path)
    import common as limpetcommon

    from carputils.testing.test import temporary_wkdir
    with temporary_wkdir(limpetdir):
        return limpetcommon.readIMPs('OFF')

(Off-topic: in the file generate.py, a module named limpetcommon is imported, but I don't know where it comes from.)

Proposal

Remove "common" from the Python 3 dependencies