Mysqldump backup should ignore warning messages

[Yang Youseok]

This is related to issue 1753498 which is to intentionally delete redirect part for mysqldump command.

But the problem is that mysqldump Warning messages are also emitted by stderr like below.

[root@56-asiaseoul-utf8 ~]# mysqldump --all-database -h 127.0.0.1 -uos_admin -pYMHpjPx8KH9DMHsFWHEqPZqAXXQrN8g9RnMB --single-transaction | gzip > t
Warning: Using unique option prefix all-database instead of all-databases is deprecated and will be removed in a future release. Please use the full name instead.
Warning: Using a password on the command line interface can be insecure.

Those messages are not literally problematic, so we have to get the similar logic catching stderr not just ignore them.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/554156

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/554932

[OpenStack Infra (hudson-openstack)]

Change abandoned by Zhao Chao (<email address hidden>) on branch: master
Review: https://review.openstack.org/554932
Reason: This should be submitted by accident, please keep updating the original one:

https://review.openstack.org/#/c/554156/

Thanks for working on this.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/554156
Committed: https://git.openstack.org/cgit/openstack/trove/commit/?id=88464d89612ae8150c73db52a4e3555961853fc1
Submitter: Zuul
Branch: master

commit 88464d89612ae8150c73db52a4e3555961853fc1
Author: Yang Youseok <email address hidden>
Date: Mon Mar 19 16:23:15 2018 +0900

    Add check_process() for mysqldump

    Before, mysqldump had redirect parts for stderr but did not have
    any check logic for that. So redirect part was deleted to avoid
    reporting which is always success.

    But, mysqldump does not emit not only errors but also warnings like
    "Warning: ..." or "[Warning] ...". This warnings should not be
    considered to error, so add check_process for filtering that like
    other backup strategies.

    Also, change message log level to debug for the right purpose and
    change print location not to print None when the output file is empty.

    Change-Id: I27b1b0628e79ca1c7b0c1ab5f939b5960ec3177a
    Close-Bug: 1756806