more diff-friendly disabling xz

Lib/tarfile.py

@@ -392,10 +392,13 @@ class _Stream:
 
             elif comptype == "xz":
                 try:
-                    # TODO: RUSTPYTHON remove underscore
-                    import lzma_
+                    import lzma
                 except ImportError:
                     raise CompressionError("lzma module is not available") from None
+
+                # XXX: RUSTPYTHON; xz is not supported yet
+                raise CompressionError("lzma module is not available") from None
+
                 if mode == "r":
                     self.dbuf = b""
                     self.cmp = lzma.LZMADecompressor()
@@ -1924,11 +1927,13 @@ class TarFile(object):
             raise ValueError("mode must be 'r', 'w' or 'x'")
 
         try:
-            # TODO: RUSTPYTHON remove underscore
-            from lzma_ import LZMAFile, LZMAError
+            from lzma import LZMAFile, LZMAError
         except ImportError:
             raise CompressionError("lzma module is not available") from None
 
+        # XXX: RUSTPYTHON; xz is not supported yet
+        raise CompressionError("lzma module is not available") from None
+
         fileobj = LZMAFile(fileobj or name, mode, preset=preset)
 
         try:

Lib/test/support/__init__.py

@@ -494,11 +494,11 @@ def requires_bz2(reason='requires bz2'):
     return unittest.skipUnless(bz2, reason)
 
 def requires_lzma(reason='requires lzma'):
-    # try:
-        # import lzma
-    # except ImportError:
-        # lzma = None
-    # TODO: RUSTPYTHON
+    try:
+        import lzma
+    except ImportError:
+        lzma = None
+    # XXX: RUSTPYTHON; xz is not supported yet
     lzma = None
     return unittest.skipUnless(lzma, reason)
 

Lib/test/test_tarfile.py

@@ -28,11 +28,11 @@ try:
 except ImportError:
     bz2 = None
 try:
-    # TODO: RUSTPYTHON
-    lzma = None
-    # import lzma
+    import lzma
 except ImportError:
     lzma = None
+# XXX: RUSTPYTHON; xz is not supported yet
+lzma = None
 
 def sha256sum(data):
     return sha256(data).hexdigest()