@effigies' and @satra's comments

Author: oesteban

nipype/interfaces/base.py

@@ -1467,11 +1467,11 @@ class must be instantiated with a command argument
     >>> cli.cmdline # doctest: +ALLOW_UNICODE
     'ls -al'
 
-    >>> pprint.pprint(cli.inputs.trait_get())  # doctest: +NORMALIZE_WHITESPACE +ALLOW_UNICODE
+    # Use get_traitsfree() to check all inputs set
+    >>> pprint.pprint(cli.inputs.get_traitsfree())  # doctest: +NORMALIZE_WHITESPACE +ALLOW_UNICODE
     {'args': '-al',
      'environ': {'DISPLAY': ':1'},
-     'ignore_exception': False,
-     'terminal_output': <undefined>}
+     'ignore_exception': False}
 
     >>> cli.inputs.get_hashval()[0][0] # doctest: +ALLOW_UNICODE
     ('args', '-al')
@@ -1638,7 +1638,7 @@ def _format_arg(self, name, trait_spec, value):
             # Depending on whether we stick with traitlets, and whether or
             # not we beef up traitlets.List, we may want to put some
             # type-checking code here as well
-            sep = trait_spec.sep or ' '
+            sep = trait_spec.sep if trait_spec.sep is not None else ' '
 
             if argstr.endswith('...'):
                 # repeatable option

nipype/pipeline/plugins/multiproc.py

@@ -139,9 +139,8 @@ def _submit_job(self, node, updatehash=False):
         self._taskid += 1
 
         # Don't allow streaming outputs
-        if hasattr(node.interface, 'terminal_output') and \
-                node.interface.terminal_output == 'stream':
-            node.interface.terminal_output = 'allatonce'
+        if getattr(node, 'terminal_output', '') == 'stream':
+            node.terminal_output = 'allatonce'
 
         self._task_obj[self._taskid] = self.pool.apply_async(
             run_node, (node, updatehash, self._taskid),