Rally does not show "missing argument" error raised by argparse while parsing cli args

[Piyush]

Consider following command- "rally verify compare"

Correct usage-
[root@piyush-104 custom_rally]# rally verify compare --uuid-1 C1 --uuid-2 C2

EXISTING BEHAVIOR-
[root@piyush-104 custom_rally]# rally verify compare
usage: rally verify compare [-h] --uuid-1 <uuid_1> --uuid-2 <uuid_2> [--csv]
                            [--html] [--json] [--output-file <output_file>]
                            [--threshold <threshold>]
                            [action_args [action_args ...]]

Compare two verification results.

optional arguments:
  -h, --help show this help message and exit
  --uuid-1 <uuid_1> UUID of the first verification
  --uuid-2 <uuid_2> UUID of the second verification
  --csv Display results in CSV format
  --html Display results in HTML format
  --json Display results in JSON format
  --output-file <output_file>
                        Path to a file to save results
  --threshold <threshold>
                        If specified, timing differences must exceed this
                        percentage threshold to be included in output

<<NO ERROR MESSAGE FOR MISSING ARGUMENT>>

EXPECTED BEHAVIOR-
Rally should also display ERROR MESSAGE saying "Missing arguments" like it does in the following case-
[root@piyush-104 custom_rally]# rally task start
Start benchmark task.

        If both task_args and task_args_file are specified, they will
        be merged. task_args has a higher priority so it will override
        values from task_args_file.
......
......
......
Command categories:
  {version,bash-completion,show,task,plugin,verify,deployment}
                        Available categories
Missing arguments: <<< ERROR MESSAGE DISPLAYED INFORMING MISSING ARGUMENT
 --task

REASON-
This happens because during "rally task start" the MissingArgs exception is raised by validate_args() function at https://github.com/openstack/rally/blob/master/rally/cli/cliutils.py#L98

However, in case of "rally verify compare", the error is thrown at https://github.com/openstack/rally/blob/master/rally/cli/cliutils.py#L473 by the argparse library itself. The code does not reach the function call validate_args().

SOLUTION-
Display missing argument based on error message at https://github.com/openstack/rally/blob/master/rally/cli/cliutils.py#L285

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/298349

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/298349
Committed: https://git.openstack.org/cgit/openstack/rally/commit/?id=9752bf0d28a2869e5ae4cbd5ef78bb8af0ac71f3
Submitter: Jenkins
Branch: master

commit 9752bf0d28a2869e5ae4cbd5ef78bb8af0ac71f3
Author: Piyush Raman Srivastava <email address hidden>
Date: Mon Mar 28 22:25:11 2016 +0530

    Show Missing Argument Error raised by Argparse

    Fix rally to display Missing Argument error raised by argparse
    during parsing of cli arguments. Refer to bug for more
    description.

    Change-Id: I0d092349dacc66d3baefa327cbf5a5cbf227e9ee
    Closes-Bug: #1562916

[Thierry Carrez (ttx)]

This issue was fixed in the openstack/rally 0.4.0 release.