Fail more clearly when tools.namespace refresh-dirs are incorrectly set

[vemv]

Context

Eastwood partly uses any set refresh-dirs. When these are badly set to e.g. non-existing or wrong-depth dirs, Eastwood fails in such a way that users can believe instead that it it's Eastwood :source-paths that are incorrectly set, or wrongly parsed.

Task

Make error-msg :namespace-filename-mismatch take a "context" i.e. a simple string explaining what Eastwood was parsing when it encountered the issue.