Don't error out with "svn: E200030: sqlite: no such table: nodes" when opening old working copies and if compiled with SVN_DEBUG. Instead, print a message advising an upgrade.
I found this problem while trying to use a format 18 WC with a trunk client.
* subversion/libsvn_wc/wc_db_wcroot.c (svn_wc__db_wcroot_parse_local_abspath): Verification triggers don't install properly with old WC format databases, so ignore sqlite errors while installing the triggers. Allows old working copies in 1.7-dev format to be upgraded to format 29 (at which point there is yet another problem which I'll investigate next).