debug output includes modulecmd output (#9476)

Debug output now includes the output of modulecmd executions. Only
output module content when a failure occurs; always report when a
module is loaded/unloaded.

lib/spack/spack/util/module_cmd.py

@@ -99,9 +99,17 @@ def get_module_cmd_from_bash(bashopts=''):
 def unload_module(mod):
     """Takes a module name and unloads the module from the environment. It does
     not check whether conflicts arise from the unloaded module"""
+    tty.debug("Unloading module: {0}".format(mod))
+
     modulecmd = get_module_cmd()
-    exec(compile(modulecmd('unload', mod, output=str, error=str), '<string>',
-                 'exec'))
+    unload_output = modulecmd('unload', mod, output=str, error=str)
+
+    try:
+        exec(compile(unload_output, '<string>', 'exec'))
+    except Exception:
+        tty.debug("Module unload output of {0}:\n{1}\n".format(
+            mod, unload_output))
+        raise
 
 
 def load_module(mod):
@@ -109,6 +117,8 @@ def load_module(mod):
     load that module. It then loads the provided module. Depends on the
     modulecmd implementation of modules used in cray and lmod.
     """
+    tty.debug("Loading module: {0}".format(mod))
+
     # Create an executable of the module command that will output python code
     modulecmd = get_module_cmd()
 
@@ -116,17 +126,28 @@ def load_module(mod):
     # We do this without checking that they are already installed
     # for ease of programming because unloading a module that is not
     # loaded does nothing.
-    text = modulecmd('show', mod, output=str, error=str).split()
-    for i, word in enumerate(text):
-        if word == 'conflict':
-            unload_module(text[i + 1])
+    module_content = modulecmd('show', mod, output=str, error=str)
+    text = module_content.split()
+    try:
+        for i, word in enumerate(text):
+            if word == 'conflict':
+                unload_module(text[i + 1])
+    except Exception:
+        tty.debug("Module show output of {0}:\n{1}\n".format(
+            mod, module_content))
+        raise
 
     # Load the module now that there are no conflicts
     # Some module systems use stdout and some use stderr
     load = modulecmd('load', mod, output=str, error='/dev/null')
     if not load:
         load = modulecmd('load', mod, error=str)
-    exec(compile(load, '<string>', 'exec'))
+
+    try:
+        exec(compile(load, '<string>', 'exec'))
+    except Exception:
+        tty.debug("Module load output of {0}:\n{1}\n".format(mod, load))
+        raise
 
 
 def get_path_arg_from_module_line(line):