rhg: Accept different "invalid ignore pattern" error message formatting

At the moment rhg compiles all patterns into a single big regular expression,
so it’s not practical to find out which file the invalid bit of syntax
came from.

Differential Revision: https://phab.mercurial-scm.org/D11942

tests/test-hgignore.t

@@ -9,10 +9,6 b''
   > EOF
 #endif
 
-TODO: fix rhg bugs that make this test fail when status is enabled
-  $ unset RHG_STATUS
-
-
   $ hg init ignorerepo
   $ cd ignorerepo
 
@@ -63,9 +59,19 b' Should display baz only:'
   ? syntax
 
   $ echo "*.o" > .hgignore
+#if no-rhg
   $ hg status
   abort: $TESTTMP/ignorerepo/.hgignore: invalid pattern (relre): *.o (glob)
   [255]
+#endif
+#if rhg
+  $ hg status
+  Unsupported syntax regex parse error:
+      ^(?:*.o)
+          ^
+  error: repetition operator missing expression
+  [255]
+#endif
 
 Ensure given files are relative to cwd