We've been notified by our automated license checker tool that argparse's License of Python v2 is incompatible with the license that we use -- the GPL.

Would you consider updating to the License of Python v2.0.1? The only difference seems like a minor technicality (but IANAL). As for earlier versions:

This is a free software license but is incompatible with the GNU GPL. The primary incompatibility is that this Python license is governed by the laws of the State of Virginia, in the USA, and the GPL does not permit this.

(from https://www.gnu.org/licenses/license-list.en.html#PythonOld)