Description of problem:

When create a new repository in quay new UI,  input a invalid repository name which include unsupported characters, the error message is just "Unable to create repository, HTTP400 - Invalid repository name." This error message isn't clear.  In current UI, the error message is "Repository names must match [a-z0-9][.a-z0-9_-](/[a-z0-9][.a-z0-9_-])* ", it is much more helpful for customer.