[Debian-astro-maintainers] Bug#1000428: gammapy: FTBFS with matplotlib 3.5

[Stefano Rivera]

Source: gammapy
Version: 0.18.2-1
Severity: serious
Justification: FTBFS

Matplotlib 3.5 seems to have caused some test failures:
=========================== short test summary info ============================
FAILED gammapy/datasets/tests/test_map.py::test_plot_residual_onoff - ValueEr...
FAILED gammapy/datasets/tests/test_spectrum.py::test_peek - TypeError: Unsupp...
FAILED gammapy/datasets/tests/test_spectrum.py::TestSpectrumOnOff::test_peek
FAILED gammapy/datasets/tests/test_spectrum.py::TestSpectrumOnOff::test_plot_fit
FAILED gammapy/irf/tests/test_edisp_map.py::test_edispkernel_from_diagonal_response
FAILED gammapy/irf/tests/test_edisp_map.py::test_edispkernel_from_1D - KeyErr...
FAILED gammapy/makers/background/tests/test_reflected.py::test_bad_on_region
FAILED gammapy/maps/tests/test_region.py::test_width - AssertionError: 
FAILED gammapy/maps/tests/test_regionnd.py::test_region_nd_map_plot - TypeErr...
FAILED gammapy/modeling/models/tests/test_spectral.py::test_model_plot - Type...
= 10 failed, 1157 passed, 479 skipped, 2 xfailed, 3 xpassed in 82.49s (0:01:22) =

With both Python 3.9 and 3.10.

See: https://buildd.debian.org/status/fetch.php?pkg=gammapy&arch=amd64&ver=0.18.2-1%2Bb1&stamp=1637623734&raw=0

SR