Inconsistent import behaviour between py_binary and par_binary about subpar

[thundergolfer]

I just ran into py_test having this same issue. Adding imports = [""] allowed for correct importing.

[aaliddell]

This may be related to bazelbuild/bazel#7067

Subpar appears to be enforcing the requirement for using fully qualified imports, whereas in py_* rules you can currently get away without the prefix. In the future there appears to be an intention to enforce similar stricter rules in the py_* rules, but it is not specified quite how that'd look or when.

Setting imports = [""] causes subpar to behave the same as the py_* rules do by adding an import path that py_* is adding by default.