When a module requirement is made of 2 alternatives, if the first alternative cannot be found but the second correctly loads an error message is still reported.
$ cat /path/to/modulefiles/bar
#%Module
$ cat /path/to/modulefiles/foo
#%Module
prereq unk bar
$ ml use /path/to/modulefiles
$ ml foo
Loading foo
ERROR: Unable to locate a modulefile for 'unk'
Loading requirement: bar
Error message should not be reported as the alternative requirement bar is successfully loaded after unk not being found.
When a module requirement is made of 2 alternatives, if the first alternative cannot be found but the second correctly loads an error message is still reported.
Error message should not be reported as the alternative requirement
bar
is successfully loaded afterunk
not being found.