tests: use inline Python for revlog test

`hg debugdata` will soon stop accepting the raw path to a revlog file.
Adjust a test accordingly.

The changed test is for a security bug. So this should be reviewed
with scrutiny.

Differential Revision: https://phab.mercurial-scm.org/D4356

tests/test-revlog.t

@@ -1,47 +1,52 b''
   $ hg init empty-repo
   $ cd empty-repo
 
 Flags on revlog version 0 are rejected
 
   >>> with open('.hg/store/00changelog.i', 'wb') as fh:
   ...     fh.write(b'\x00\x01\x00\x00') and None
 
   $ hg log
   abort: unknown flags (0x01) in version 0 revlog 00changelog.i!
   [255]
 
 Unknown flags on revlog version 1 are rejected
 
   >>> with open('.hg/store/00changelog.i', 'wb') as fh:
   ...     fh.write(b'\x00\x04\x00\x01') and None
 
   $ hg log
   abort: unknown flags (0x04) in version 1 revlog 00changelog.i!
   [255]
 
 Unknown version is rejected
 
   >>> with open('.hg/store/00changelog.i', 'wb') as fh:
   ...     fh.write(b'\x00\x00\x00\x02') and None
 
   $ hg log
   abort: unknown version (2) in revlog 00changelog.i!
   [255]
 
   $ cd ..
 
 Test for CVE-2016-3630
 
   $ hg init
 
   >>> open("a.i", "wb").write(
   ... b"""eJxjYGZgZIAAYQYGxhgom+k/FMx8YKx9ZUaKSOyqo4cnuKb8mbqHV5cBCVTMWb1Cwqkhe4Gsg9AD
   ... Joa3dYtcYYYBAQ8Qr4OqZAYRICPTSr5WKd/42rV36d+8/VmrNpv7NP1jQAXrQE4BqQUARngwVA=="""
   ... .decode("base64").decode("zlib"))
 
   $ hg debugindex a.i
      rev linkrev nodeid       p1           p2
        0       2 99e0332bd498 000000000000 000000000000
        1       3 6674f57a23d8 99e0332bd498 000000000000
-  $ hg debugdata a.i 1 2>&1 | egrep 'Error:.*decoded'
-  (mercurial\.\w+\.mpatch\.)?mpatchError: patch cannot be decoded (re)
+
+  >>> from mercurial import revlog, vfs
+  >>> tvfs = vfs.vfs(b'.')
+  >>> tvfs.options = {b'revlogv1': True}
+  >>> rl = revlog.revlog(tvfs, b'a.i')
+  >>> rl.revision(1)
+  mpatchError('patch cannot be decoded',)