Improve error handling in `getRevision`

[massonju]

In getRevision we catch all exception errors and display this error:

    except Exception as e:
        with redirect_stdout(sys.stderr):
            print('Cannot fetch project {}/{}'.format(remoteUrl, project))
            print(e)

However we may have different errors not related to a fetch issue.

Example: if the rev is not present in the revision dictionary, we raise an exception which is not a fetch issue

The error handling of this function can be improved.