Improve external package location detection algorithm. (#5145)

Also inspect `PATH` to help locate an external package and provide a test for
getting path from module's PATH.

Fixes #5141

lib/spack/spack/test/module_parsing.py

@@ -53,7 +53,8 @@ def test_get_path_from_module(save_env):
     lines = ['prepend-path LD_LIBRARY_PATH /path/to/lib',
              'setenv MOD_DIR /path/to',
              'setenv LDFLAGS -Wl,-rpath/path/to/lib',
-             'setenv LDFLAGS -L/path/to/lib']
+             'setenv LDFLAGS -L/path/to/lib',
+             'prepend-path PATH /path/to/bin']
 
     for line in lines:
         module_func = '() { eval `echo ' + line + ' bash filler`\n}'

lib/spack/spack/util/module_cmd.py

@@ -187,6 +187,12 @@ def get_path_from_module(mod):
         if L >= 0:
             return line[L + 2:line.find('/lib')]
 
+    # If it sets the PATH, use it
+    for line in text:
+        if line.find('PATH') >= 0:
+            path = get_argument_from_module_line(line)
+            return path[:path.find('/bin')]
+
     # Unable to find module path
     return None