Fix for - in session labels???

[duettwe]

Have a project (AdolRisk; 02/23-02/24 logs) that tried putting - in the session label, rather than _. This caused the project to fail to build and didn't provide any real insight on to what was happening. When we switched over to _, it started working. It appears to be the part of the code that is extracting project, subject, session labels under the "attr" section of the yaml.

We've previously seen no issue with - in SUBJECT labels (i.e. HeckersESOP).

Is this something we should fix or a 'rule' that only underscores are allowed in session labels?