Revert "parse error."

This reverts commit 068757da79b7992a176a4fe2aff31acd057a515a.
Revert "Skip the tag migrations if the Content migration has not been run."

This reverts commit 08f604012bf1c8094bc88cea655bdc460d62ccfb.

Doh. This obviously is incorrect, as it assumes a SQL backend for the
Content system and needs knowledge of the inner workings of it.