Error exit code set when one requirement fails to load however alternative requirement is loaded #510

When a module defines a N-module requirement, if one of these module loads successfully the requirement is satisfied.

However, if one module fails then one of the other succeed to load, an error exit code is still set.

$ cat /path/to/modulefiles/quz
#%Module
break
$ cat /path/to/modulefiles/bar
#%Module
$ cat /path/to/modulefiles/foo
#%Module
prereq quz bar
$ ml use /path/to/modulefiles
$ ml foo
Loading foo
  Loading requirement: bar
$ echo $?
1

No error exit code should be set as one module satisfying the requirement has been loaded.