Fix the known-bug tests on debug builds and zlib-ng

The test pinning gh-160001 expects a SystemError, but in a debug build
the missing exception trips a C assertion in the call machinery before
the SystemError is raised, which aborts the test worker.  All CI builds
are debug builds, so the test is skipped there until the bug is fixed.

The gzip examples for gh-159999 also depend on where inflate stops
consuming input, and none of them triggered the bug with zlib-ng, which
the Windows builds use.  This adds an example found against zlib-ng
2.2.4 in zlib-compat mode; the zlib wrapper and raw deflate examples
already fail with both libraries.

The comments now also reference the filed issues.

Author: pganssle

Lib/test/test_compression_property.py

@@ -457,7 +457,8 @@ def test_invalid_input(self, garbage, data, index, byte, sizes,
 
 class _BZ2NeedsInputBug:
     # bz2 reports needs_input=True as soon as its input buffer is empty, even
-    # when max_length cut the output short and more of it is pending.
+    # when max_length cut the output short and more of it is pending
+    # (gh-159999).
     @unittest.expectedFailure
     @hypothesis.given(
         data=data_strategy,
@@ -470,8 +471,11 @@ def test_needs_input_means_drained(self, data, sizes, max_lengths):
 
 
 class _ZlibNeedsInputBug:
-    # zlib._ZlibDecompressor has the same needs_input problem as bz2.  One
-    # example per wbits variant: zlib wrapper, raw deflate, gzip wrapper.
+    # zlib._ZlibDecompressor has the same needs_input problem as bz2
+    # (gh-159999).  The examples depend on where the compressor puts block
+    # boundaries, so there are several: at least one must fail for each
+    # wbits variant (zlib wrapper, raw deflate, gzip wrapper) with both zlib
+    # and zlib-ng.
     @unittest.expectedFailure
     @hypothesis.given(
         data=data_strategy,
@@ -486,15 +490,20 @@ class _ZlibNeedsInputBug:
         sizes=[34],
         max_lengths=[20],
     )
+    @hypothesis.example(
+        data=b"\x00\x00\x00\x00\x01\x00\x00\x00\x02\x00\x00\x03" * 2,
+        sizes=[25],
+        max_lengths=[12],
+    )
     def test_needs_input_means_drained(self, data, sizes, max_lengths):
         self._check_needs_input_means_drained(data, sizes, max_lengths)
 
 
 # liblzma reports an error when two consecutive calls can make no progress,
 # which lzma.LZMADecompressor lets through as LZMAError("Insufficient buffer
-# space") for two max_length=0 calls in a row with nothing buffered.  The
-# broad lzma tests avoid max_length=0 so that they keep checking everything
-# else; test_repeated_max_length_zero pins the bug.
+# space") for two max_length=0 calls in a row with nothing buffered
+# (gh-160000).  The broad lzma tests avoid max_length=0 so that they keep
+# checking everything else; test_repeated_max_length_zero pins the bug.
 lzma_max_length_strategy = st.integers(1, 64) | st.just(-1)
 lzma_max_lengths_strategy = st.lists(lzma_max_length_strategy, max_size=16)
 
@@ -784,7 +793,10 @@ def test_raw_deflate(self, data, zdict, level):
 
     # _ZlibDecompressor only applies zdict up front for raw deflate; for a
     # zlib-wrapped stream it hits Z_NEED_DICT and returns NULL without
-    # setting an exception, which surfaces as SystemError.
+    # setting an exception (gh-160001).  That surfaces as SystemError in a
+    # release build and as a fatal C assertion in a debug build, so the test
+    # can only run in the former.
+    @unittest.skipIf(support.Py_DEBUG, "gh-160001 aborts debug builds")
     @unittest.expectedFailure
     @hypothesis.given(
         data=data_strategy,