tests: ignore test-storage when using Rust

This is only relevant for Python code and the SQLite backend, which is in a
half-abandoned state.

tests/test-storage.py

@@ -15,6 +15,17 b' from mercurial import ('
 from mercurial.testing import storage as storagetesting
 
 try:
+    from mercurial import rustext
+
+    rustext.__name__
+    # Does not pass with pure Rust index
+    import sys
+
+    sys.exit(80)
+except ImportError:
+    pass
+
+try:
     from hgext import sqlitestore
 except ImportError:
     sqlitestore = None