Program received signal SIGSEGV, Segmentation fault.
0x00007fffecadc34b in Triangulation::is_masked (this=this@entry=0x27e07e0, tri=tri@entry=1) at lib/matplotlib/tri/_tri.cpp:533
533         return !_mask.empty() && _mask(tri);
(gdb) bt
#0  0x00007fffecadc34b in Triangulation::is_masked (this=this@entry=0x27e07e0, tri=tri@entry=1) at lib/matplotlib/tri/_tri.cpp:533
#1  0x00007fffecae0c0c in Triangulation::calculate_neighbors (this=this@entry=0x27e07e0) at lib/matplotlib/tri/_tri.cpp:343
#2  0x00007fffecae1e46 in Triangulation::get_neighbors (this=0x27e07e0) at lib/matplotlib/tri/_tri.cpp:498
#3  0x00007fffecae7dbe in PyTriangulation_get_neighbors (self=<optimized out>, args=<optimized out>, kwds=<optimized out>)
    at lib/matplotlib/tri/_tri_wrapper.cpp:142
#4  0x00007ffff7aefdb9 in call_function (oparg=<optimized out>, pp_stack=0x7ffffffc2bc8) at Python/ceval.c:4017
#5  PyEval_EvalFrameEx (f=<optimized out>, throwflag=<optimized out>) at Python/ceval.c:2679

[  -- snipped 1.6k (?!) calls in ceval.c -- ]