When upgrading to 5.2. The /etc/shells file is changed and
set to a value which does not contain (at least) /bin/zsh.
PS: This is probably not a zsh problem, but /etc/shells
doesn't seem to belong to any package.
I did an upgrade from 5.1 to 5.2 and this file was not changed. Also
it does not contain an entry for /bin/zsh in either 5.1 or 5.2
*** This bug has been marked as a duplicate of 365 ***