You shouldn't use enewgroup and enewuser in src_install(). Please run it in pkg_setup or postinst functions.
ATM It's needed by stuff in src_install() , the first time you install mysql. Most of this stuff is duplicated in pkg_postinst(), so it should not be needed however there was a pair of hard to die bugs in the past and I want to dig it better. those function will return in pkg_setup after that is ready.
Fixed, In CVS, with a bunch of other cosmetic fixes.