Provide a slightly more descriptive error message
@@ -61,7 +61,7 @@ class GitHubRepoProvider(RepoProvider):
super().__init__(*args, **kwargs)
spec_parts = self.spec.split('/')
if len(spec_parts) != 3:
- raise ValueError('Spec is not of form username/repo/branch')
+ raise ValueError('Spec is not of form username/repo/branch, provided {spec}'.format(spec=spec))
self.user, self.repo, self.unresolved_ref = spec_parts
if self.repo.endswith('.git'):
