expat-2.6.0 breaks pythonXX build

[dmacks]

Python-upstream confirms there are test-failures due to the just-released expat-2.6.0 and has fixes. python/cpython#115133

Originally posted by @dmacks in #996 (comment)

[dmacks]

Upstream has fixed python38 and above, so we can grab their patches:

• python310 (fixed via 892af6c upstream patch)
• python39 (fixed via 892af6c upstream patch)
• python38 (fixed via 892af6c upstream patch)

Several suits of packages and a few one-offs are hardcoded to python37, so we should look at backporting a fix there:

• python37 (fixed via 1d595f1 py38's upstream patch)

Fink has dist-restricted python{34,35,36} to OS X 10.15 and below. Should we bother keeping 34/35/36 limping along by trying to backport upstream's fixes for newer pythonXX, or use this as a chance to kill them outright?

• python36 (fixed via 6b5d07e disabling 'test_xml_etree' and 'test_xml_etree_c' and backporting newer test_minidom)
• python35 (fixed via 6b5d07e disabling 'test_xml_etree' and 'test_xml_etree_c' and backporting newer test_minidom)
• python34 (fixed via c80bf1d disabling 'test_xml_etree' and 'test_xml_etree_c' and backporting newer test_minidom)

Some packages are pinned to python27, so we should look at backporting a fix there:

• python27 (7eb1bf8 makes things better not worse, but they have always been bad)

[dmacks]

Upstream patch does not apply cleanly to 36 and below (nor to 27's, where the test failure looks different also)

[nieder]

py34-36 are already dist restricted. If they can't be patched for this failure with only minimal effort, then the test can be easily skipped. That's less effort than deleting python3[456].info and modifying all existing *-py.info to remove relevant variants. Is there any indication that expat-2.6 breaks actual python function or just tickles that test?

[dmacks]

Python36 and below also are failing test_minidom; again looks like a test bug, as copying that test suite from newer pythonXX clears it on python{35,36}. On older, it doesn't apply as cleanly...still working on it.