Improve lago collect error handling

1. Don't display the entire stack trace on error (but still write
   it to the log). This was achieved by making VMError a subclass of
   LagoException.

2. When ignoring missing files, explain why.

3. Make the error message of ExtractPathNoPathError more informative.

4. Don't propagate errors to the outer log task when ignoring missing
   files, thus avoid false positives on stdout.

Signed-off-by: gbenhaim <[email protected]>

lago/plugins/vm.py

@@ -49,7 +49,7 @@
 LogTask = functools.partial(log_utils.LogTask, logger=LOGGER)
 
 
-class VMError(Exception):
+class VMError(utils.LagoException):
     pass
 
 
@@ -58,7 +58,8 @@ class ExtractPathError(VMError):
 
 
 class ExtractPathNoPathError(VMError):
-    pass
+    def __init__(self, err):
+        super().__init__('Failed to extract files: {}'.format(err))
 
 
 class LagoVMNotRunningError(utils.LagoUserException):
@@ -265,11 +266,14 @@ def _extract_paths_scp(self, paths, ignore_nopath):
                 self.vm.copy_from(
                     local_path=guest_path,
                     remote_path=host_path,
-                    propagate_fail=False
+                    propagate_fail=not ignore_nopath
                 )
             except ExtractPathNoPathError as err:
                 if ignore_nopath:
-                    LOGGER.debug('%s: ignoring', err.args[0])
+                    LOGGER.debug(
+                        '%s: ignoring since ignore_nopath was set to True',
+                        err.args[0]
+                    )
                 else:
                     raise
 
@@ -417,6 +421,7 @@ def copy_from(
     ):
         with LogTask(
             'Copy from %s:%s to %s' % (self.name(), remote_path, local_path),
+            propagate_fail=propagate_fail
         ):
             try:
                 with self._scp(propagate_fail=propagate_fail) as scp: