opened
bolkedebruin
username_0
Make sure you have checked _all_ steps below.

### JIRA
- [X] My PR addresses the following [Airflow JIRA](https://issues.apache.org/jira/browse/AIRFLOW/) issues and references them in the PR title. For example, "[AIRFLOW-XXX] My Airflow PR"
    - https://issues.apache.org/jira/browse/AIRFLOW-XXX


### Description
- [ ] Here are some details about my PR, including screenshots of any UI changes:

While @once with catchup=False don't make sense,
the scheduler could schedule these kind of dags
due to a logic error.
### Tests
- [X] My PR adds the following unit tests __OR__ does not need testing for this extremely good reason:

* New tests added.


### Commits
- [X] My commits all reference JIRA issues in their subject lines, and I have squashed multiple commits if they address the same issue. In addition, my commits follow the guidelines from "[How to write a good git commit message](http://chris.beams.io/posts/git-commit/)":
    1. Subject is separated from body by a blank line
    2. Subject is limited to 50 characters
    3. Subject does not end with a period
    4. Subject uses the imperative mood ("add", not "adding")
    5. Body wraps at 72 characters
    6. Body explains "what" and "why", not "how"

- [X] Passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
[AIRFLOW-1928] Fix @once with catchup=False
issue
created
bolkedebruin
username_0
cc @jgao54
comment