Created attachment 901728 [details]
promoting a CV to next env, when a promotion already ongoing for another env, raised ISE error in production.log

Description of problem:
I created environments for promoting CV's: like

Library-->dev--> test

I created a CV and published it to 'Library' env. And later I promoted it to next env "dev". So when the promotion was on-going for "dev", I tried to promote same CV to next env "test". And UI throws following error:

---
Required lock is already taken by other running tasks. Please inspect their state, fix their errors nad resume them. Required lock: read Conflicts with tasks: - https://dhcp207-55.lab.eng.pnq.redhat.com/foreman_tasks/tasks/595cf53f-1daa-4d4a-91ff-d7331eb492e5 
---

I know that its expected since a promotion is already on-going. But I think we should make the error message more clear?
OR
we should disable the promote button when a promotion is already on-going ?
AND
In any case, "Internal server Error" shouldn't be thrown in production.log


Version-Release number of selected component (if applicable):
sat6 beta sanp7 compose2 (Satellite-6.0.3-RHEL-6-20140528.4)

How reproducible:
always

Steps to Reproduce:
1. create env for promoting CV's: like
Library-->dev--> test
2. create a CV and publish it
3. Now promote it to next env "dev"
4. when promotion to "dev" is ongoing, again try to promote and select env "test"


Actual results:
UI throws:
---
Required lock is already taken by other running tasks. Please inspect their state, fix their errors nad resume them. Required lock: read Conflicts with tasks: - https://dhcp207-55.lab.eng.pnq.redhat.com/foreman_tasks/tasks/595cf53f-1daa-4d4a-91ff-d7331eb492e5 
---

500 Internal Server Error in production.log


Expected results:
1. In any case, "Internal server Error" shouldn't be thrown in production.log
2. The raised message should be more clear from end user perspective. Promotion to "env" is already in-progress, please wait until the current promotion is finished..somthing like this ?
3. The best would be, disable the promote button when a promotion is already on-going ?

Additional info: