Latest commit b87fca2 Mar 25, 2017 @eric-wieser eric-wieser MAINT: Remove asbytes where a b prefix would suffice
Since we only need to support python 2, we can remove any case where we just
pass a single string literal and use the b prefix instead.

What we can't do is transform asbytes("tests %d" % num), because %-formatting
fails on bytes in python 3.x < 3.5.