Unable to manually trigger master-build when "except" is used.
### Summary
Having following rudimentary ".gitlab-ci.yml":
```
stages:
- setup
- build
- package
- deploy
setup-frontend:
stage: setup
except:
changes:
- ".gitlab-ci.yml"
script:
- echo foo
```
i try to manually trigger a "master"-branch build using "Pipepines"-"Run pipeline"-Button in the WebUI.
The pipeline start fails with following error:
If i do comment out the "except:" section (lines 10-12 in https://gitlab.com/v2b1n/test/blob/master/.gitlab-ci.yml) then i can start the pipeline normally.
### Steps to reproduce
Use the mentioned .gitlab-ci.yml and try to start a Pipeline on a "master"-branch using "Pipepines"-"Run pipeline"-Button.
If i do comment out the "except:" section (lines 10-12 in https://gitlab.com/v2b1n/test/blob/master/.gitlab-ci.yml) then i can start the pipeline normally.
### Example Project
https://gitlab.com/v2b1n/test/pipelines
### What is the current *bug* behavior?
The pipeline does not start.
### What is the expected *correct* behavior?
The pipeline should start.
### Relevant logs and/or screenshots
### Output of checks
This bug happens on GitLab.com.
I also was able to reproduce this behaviour in v11.11.8 of self-managed gitlab foss instance.
issue