fix:[1] Unify error objects with GitHub errors.

[yuichi10]

Context

Scms are using different error objects and API does not handle GitLab error objects.
e.g. https://github.com/screwdriver-cd/screwdriver/blob/master/plugins/webhooks/index.js#L405

These errors should be handled by API.

Objective

• Error object has status property instead of code property.

References

screwdriver-cd/screwdriver#2367
screwdriver-cd/scm-bitbucket#75

License

I confirm that this contribution is made under the terms of the license found in the root directory of this repository's source tree and that I have the authority necessary to make this contribution on behalf of its copyright owner.

[itleigns]

Do we also need to check error.status here?

scm-gitlab/test/index.test.js

Line 215 in 8662afa

});

[itleigns]

Same as above.

scm-gitlab/test/index.test.js

Line 238 in 8662afa

});

[kkisic]

Do we also need to check error.status here?

scm-gitlab/test/index.test.js

Line 215 in 8662afa

});

I fixed it.