BUG: runtests: make -t option work again
Merge pull request #3949 from charris/backport-1.8-3948

backport-1.8-3948
MAINT: io: handle a bad fmt argument in savetxt by raising a ValueError.
Merge pull request #3956 from charris/backport-1.8-3953

backport-1.8-3953