When removing support for dotkit in #11986 the code trying to set the
paths of the various module files was not updated to skip it. This
results in a failure because of a key error after the deprecation
warning is displayed to user.
This commit fixes the issue and adds a unit test for regression.
Note that code for Spack chains has been updated accordingly but
no unit test has been added for that case.
6a1021b81c