Re-enable use of the CKAN_INI environment variable.

[davidread]

It's really handy to use CKAN_INI environment variable for specifying where your development.ini is, for paster commands.

This was originally implemented in #2005 in Nov 2014 but got blown out at some point - I think the default='development.ini' got added back in by a duff merge.

Also: Improve error message when there is no config specified.

Test

(default)vagrant@vagrant-ubuntu-trusty-64:~$ paster --plugin=ckan user admin -c /etc/ckan/default/development.ini
<works>
(default)vagrant@vagrant-ubuntu-trusty-64:~$ paster --plugin=ckan user admin
ERROR: You need to specify the CKAN config (.ini) file path.
Use the --config parameter or set environment variable CKAN_INI or have development.ini
in the current directory.
(default)vagrant@vagrant-ubuntu-trusty-64:~$ export CKAN_INI=/etc/ckan/default/development.ini
(default)vagrant@vagrant-ubuntu-trusty-64:~$ paster --plugin=ckan user admin
<works>

[davidread]

@KrzysztofMadejski I don't suppose you could test this, since you showed interest in using it?

[KrzysztofMadejski]

I was interested in it, also for archiver's celery tasks. I'll try to test it tomorrow.

[smotornyuk]

I tested it - everything just work fine

[davidread]

Great! What happens next - do you merge it or reassign to someone who can?