frontend: report arguments errors with better detail

When reporting argument errors, show also a context -- what is processed,
what is the name of the command.

2 files changed, 3 insertions, 2 deletions

diff --git a/ipalib/frontend.py b/ipalib/frontend.py
index cac3e3b3..f478ef09 100644
--- a/ipalib/frontend.py
+++ b/ipalib/frontend.py
@@ -869,7 +869,8 @@ class Command(HasParam):
         for arg in args():
             if optional and arg.required:
                 raise ValueError(
-                    '%s: required argument after optional' % arg.name
+                    '%s: required argument after optional in %s arguments %s' % (arg.name,
+                    self.name, map(lambda x: x.param_spec, args()))
                 )
             if multivalue:
                 raise ValueError(
diff --git a/ipatests/test_ipalib/test_frontend.py b/ipatests/test_ipalib/test_frontend.py
index 310d7a53..ce943a7e 100644
--- a/ipatests/test_ipalib/test_frontend.py
+++ b/ipatests/test_ipalib/test_frontend.py
@@ -280,7 +280,7 @@ class test_Command(ClassChecker):
 
         # Test ValueError, required after optional:
         e = raises(ValueError, self.get_instance, args=('arg1?', 'arg2'))
-        assert str(e) == 'arg2: required argument after optional'
+        assert str(e) == "arg2: required argument after optional in %s arguments ['arg1?', 'arg2']" % (self.get_instance().name)
 
          # Test ValueError, scalar after multivalue:
         e = raises(ValueError, self.get_instance, args=('arg1+', 'arg2'))