Print debugging info when a subcommand fails, even when ignore_errors…

… is true.

When a subcommand gives an error and ignore_errors is false, we die with
the error output.  But when ignore_errors is true, there's no way to see
the error output, even when running with -d.  This change fixes that but
emitting the error output in debug mode.

I also changed the log messages a bit when running a command, to make it
clear that we're running a subcommand.

Reviewed at http://reviews.reviewboard.org/r/3007/

rbtools/utils/process.py

@@ -31,9 +31,9 @@ def execute(command,
     Utility function to execute a command and return the output.
     """
     if isinstance(command, list):
-        logging.debug(subprocess.list2cmdline(command))
+        logging.debug('Running: ' + subprocess.list2cmdline(command))
     else:
-        logging.debug(command)
+        logging.debug('Running: ' + command)
 
     if env:
         env.update(os.environ)
@@ -74,6 +74,9 @@ def execute(command,
 
     if rc and not ignore_errors and rc not in extra_ignore_errors:
         die('Failed to execute command: %s\n%s' % (command, data))
+    elif rc:
+        logging.debug('Command exited with rc %s: %s\n%s---'
+                      % (rc, command, data))
 
     if rc and none_on_ignored_error:
         return None