TST: matplotlib.checkdep_usetex is deprecated, what to do?

[pllim]

astropy/astropy/visualization/wcsaxes/tests/test_misc.py

Lines 28 to 30 in e7f5d50

	# We cannot use matplotlib.checkdep_usetex() anymore, see
	# https://github.com/matplotlib/matplotlib/issues/23244
	TEX_UNAVAILABLE = True

was

TEX_UNAVAILABLE = not matplotlib.checkdep_usetex(True)

But it has been deprecated by matplotlib, see matplotlib/matplotlib#23244 . We either have to "vendor the code" or find another way to detect this test case. For now, the test depending on this is completely disabled (#13322).

cc @Cadair and @astrofrog

[oscargus]

As discussed in the Matplotlib issue, feel free to either copy the code or use the private method (and hope that it is not removed or changes functionality later, which seems unlikely but no guarantees).

[astrofrog]

We should check what happens to the tests if tex is indeed unavailable and we don't skip them - is there an exception or warning we could check that meant that tex was not available?