MNT: suppress pytest-mpl warning for unregistered marker
MNT: suppress pytest-mpl warning for unregistered marker

see matplotlib/pytest-mpl#69

dopplershift/MetPy,Unidata/MetPy,dopplershift/MetPy,ahaberlie/MetPy,Unidata/MetPy,ShawnMurd/MetPy,ahaberlie/MetPy