The test failures illustrate that there are other classes in pip reliant on the lenience of Distribution not enforcing its abstractmethods and these issues weren't caught earlier because pip doesn't test against importlib_metadata.

I'll proceed to merge this change, but I'll be happy to entertain any review comments and will amend or roll back the changes as needed.

⚠️⚠️⚠️ Buildbot failure⚠️⚠️⚠️

Hi! The buildbotAMD64 Windows10 3.x has failed when building commit3e0fec7.

What do you need to do:

1. Don't panic.
2. Checkthe buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/all/#builders/146/builds/4915) and take a look at the build logs.
4. Check if the failure is related to this commit (3e0fec7) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/all/#builders/146/builds/4915

Failed tests:

• test_importlib

Failed subtests:

• test_read_text - test.test_importlib.test_metadata_api.APITests.test_read_text

Summary of the results of the build (if available):

== Tests result: FAILURE then FAILURE ==

399 tests OK.

10 slowest tests:

• test_math: 6 min 34 sec
• test_asyncio: 4 min 43 sec
• test_tokenize: 3 min 42 sec
• test_multiprocessing_spawn: 3 min 41 sec
• test_lib2to3: 2 min 52 sec
• test_capi: 2 min 30 sec
• test_unparse: 1 min 57 sec
• test_concurrent_futures: 1 min 46 sec
• test_unicodedata: 1 min 42 sec
• test_compileall: 1 min 33 sec

1 test failed:
test_importlib

34 tests skipped:
test_clinic test_curses test_dbm_gnu test_dbm_ndbm test_devpoll
test_epoll test_fcntl test_fork1 test_gdb test_grp test_ioctl
test_kqueue test_multiprocessing_fork
test_multiprocessing_forkserver test_nis test_openpty
test_ossaudiodev test_peg_generator test_perf_profiler test_pipes
test_poll test_posix test_pty test_pwd test_readline test_resource
test_spwd test_syslog test_threadsignals test_wait3 test_wait4
test_xxlimited test_xxtestfuzz test_zipfile64

1 re-run test:
test_importlib

Total duration: 20 min 48 sec

Traceback (most recent call last):  File"D:\buildarea\3.x.bolen-windows10\build\Lib\test\test_importlib\test_metadata_api.py", line86, intest_read_text    top_level= [^IndexError:list index out of range

⚠️⚠️⚠️ Buildbot failure⚠️⚠️⚠️

Hi! The buildbotARM64 Windows 3.x has failed when building commit3e0fec7.

What do you need to do:

1. Don't panic.
2. Checkthe buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/all/#builders/729/builds/4192) and take a look at the build logs.
4. Check if the failure is related to this commit (3e0fec7) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/all/#builders/729/builds/4192

Failed tests:

• test_importlib

Failed subtests:

• test_read_text - test.test_importlib.test_metadata_api.APITests.test_read_text

Summary of the results of the build (if available):

== Tests result: FAILURE then FAILURE ==

396 tests OK.

10 slowest tests:

• test_math: 6 min 45 sec
• test_asyncio: 6 min 2 sec
• test_multiprocessing_spawn: 4 min 45 sec
• test_tokenize: 3 min 59 sec
• test_lib2to3: 3 min 19 sec
• test_unparse: 2 min 32 sec
• test_capi: 1 min 57 sec
• test_fstring: 1 min 56 sec
• test_concurrent_futures: 1 min 50 sec
• test_unicodedata: 1 min 47 sec

1 test failed:
test_importlib

37 tests skipped:
test_clinic test_curses test_dbm_gnu test_dbm_ndbm test_devpoll
test_epoll test_fcntl test_fork1 test_gdb test_grp test_ioctl
test_kqueue test_multiprocessing_fork
test_multiprocessing_forkserver test_nis test_openpty
test_ossaudiodev test_peg_generator test_perf_profiler test_pipes
test_poll test_posix test_pty test_pwd test_readline test_resource
test_spwd test_syslog test_threadsignals test_tix test_tkinter
test_ttk test_wait3 test_wait4 test_xxlimited test_xxtestfuzz
test_zipfile64

1 re-run test:
test_importlib

Total duration: 21 min 44 sec

Traceback (most recent call last):  File"C:\Workspace\buildarea\3.x.linaro-win-arm64\build\Lib\test\test_importlib\test_metadata_api.py", line86, intest_read_text    top_level= [^IndexError:list index out of range

⚠️⚠️⚠️ Buildbot failure⚠️⚠️⚠️

Hi! The buildbotARM64 Windows Non-Debug 3.x has failed when building commit3e0fec7.

What do you need to do:

1. Don't panic.
2. Checkthe buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/all/#builders/730/builds/7452) and take a look at the build logs.
4. Check if the failure is related to this commit (3e0fec7) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/all/#builders/730/builds/7452

Failed tests:

• test_importlib

Failed subtests:

• test_read_text - test.test_importlib.test_metadata_api.APITests.test_read_text

Summary of the results of the build (if available):

== Tests result: FAILURE then FAILURE ==

397 tests OK.

10 slowest tests:

• test_asyncio: 3 min 19 sec
• test_multiprocessing_spawn: 2 min 8 sec
• test_concurrent_futures: 1 min 16 sec
• test_socket: 1 min 8 sec
• test_math: 48.9 sec
• test_mmap: 45.9 sec
• test_urllib2_localnet: 44.6 sec
• test_tokenize: 40.8 sec
• test_io: 39.4 sec
• test_hashlib: 34.6 sec

1 test failed:
test_importlib

36 tests skipped:
test_clinic test_curses test_dbm_gnu test_dbm_ndbm test_devpoll
test_epoll test_fcntl test_fork1 test_gdb test_grp test_ioctl
test_kqueue test_multiprocessing_fork
test_multiprocessing_forkserver test_nis test_openpty
test_ossaudiodev test_peg_generator test_perf_profiler test_pipes
test_poll test_posix test_pty test_pwd test_readline test_resource
test_spwd test_syslog test_threadsignals test_tix test_tkinter
test_ttk test_wait3 test_wait4 test_xxtestfuzz test_zipfile64

1 re-run test:
test_importlib

Total duration: 8 min 21 sec

Traceback (most recent call last):  File"C:\Workspace\buildarea\3.x.linaro-win-arm64.nondebug\build\Lib\test\test_importlib\test_metadata_api.py", line86, intest_read_text    top_level= [^IndexError:list index out of range

⚠️⚠️⚠️ Buildbot failure⚠️⚠️⚠️

Hi! The buildbotAMD64 Windows11 Bigmem 3.x has failed when building commit3e0fec7.

What do you need to do:

1. Don't panic.
2. Checkthe buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/all/#builders/1079/builds/1059) and take a look at the build logs.
4. Check if the failure is related to this commit (3e0fec7) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/all/#builders/1079/builds/1059

Failed tests:

• test_importlib

Failed subtests:

• test_read_text - test.test_importlib.test_metadata_api.APITests.test_read_text

Summary of the results of the build (if available):

== Tests result: FAILURE then FAILURE ==

399 tests OK.

10 slowest tests:

• test_bigmem: 51 min 57 sec
• test_lzma: 31 min 55 sec
• test_bz2: 21 min 15 sec
• test_array: 8 min 57 sec
• test_zlib: 4 min 49 sec
• test_hashlib: 3 min 58 sec
• test_asyncio: 3 min 35 sec
• test_multiprocessing_spawn: 2 min 10 sec
• test_math: 1 min 39 sec
• test_pickle: 1 min 17 sec

1 test failed:
test_importlib

34 tests skipped:
test_clinic test_curses test_dbm_gnu test_dbm_ndbm test_devpoll
test_epoll test_fcntl test_fork1 test_gdb test_grp test_ioctl
test_kqueue test_multiprocessing_fork
test_multiprocessing_forkserver test_nis test_openpty
test_ossaudiodev test_peg_generator test_perf_profiler test_pipes
test_poll test_posix test_pty test_pwd test_readline test_resource
test_spwd test_syslog test_threadsignals test_wait3 test_wait4
test_xxlimited test_xxtestfuzz test_zipfile64

1 re-run test:
test_importlib

Total duration: 1 hour 2 min

Traceback (most recent call last):  File"R:\buildarea\3.x.ambv-bb-win11.bigmem\build\Lib\test\test_importlib\test_metadata_api.py", line86, intest_read_text    top_level= [^IndexError:list index out of range

I'm investigating these now.

Failure message is:

======================================================================ERROR: test_read_text (test.test_importlib.test_metadata_api.APITests.test_read_text) [egg_with_no_modules-pkg]----------------------------------------------------------------------Traceback (most recent call last):  File "D:\buildarea\3.x.bolen-windows10\build\Lib\test\test_importlib\test_metadata_api.py", line 86, in test_read_text    top_level = [                ^IndexError: list index out of range----------------------------------------------------------------------

The tests are failing on Windows buildbots, but I struggle to think of what might be different about the buildbot environments that would affect this test.

I'm also unsure how to replicate the failure. Tests clearly pass on Windows in general. What is it about this test that makes it fail in the buildbot environments only? Since I don't have a way to triage the failure further, I'm going to mark the test as "xfail" for now to stop the buildbot failures.