Description:

 It's better to use "Field is required" rather than format not matched error message

How reproducible:

100%

Steps:

1. Launch OSD creation wizard
2. Fill in required elements and switch to "Machine pool" step
3. Expand "Edit node labels"
4. Fill in label value without filling label key
5. Click next button

Actual result:

It shows error message of "A valid key name must consist of alphanumeric characters, '-', '.' or '_' and must start and end with an alphanumeric character"

Expect result:

 It's better to use "Field is required" rather than format not matched error message