dev-python/numpy-1.17.4-r3 got stable but has no python2_7 as PYTHON_TARGETS, however current stable matplotlib is 2.2.2-r1, which has python2_7 in PYTHON_TARGETS by default and depends on numpy.
This bug would be solved by the stabilization request bug 714376, as matplotlib-3.1.2 drops python2_7.
Yes. No need for a duplicate...
*** This bug has been marked as a duplicate of bug 714376 ***
I wasn't sure whether this is an exact duplicate. Inkscape, for instance, depends on on numpy or numpy-python2. Hence I got the impression that matplotlib-2.2.2-r1 could be "fixed" independently of bug 714376.