Fix uncaught error when parsing rest headers, document Started this work as better docs for rest response format. But I found 406 error response was not being tested. Also there was no error for bad Content-Type. In rest.py fix uncaught exceptions due to invalid Accept or Content-Type headers. If Content-type is valid but not application/json return code 415. Document use of accept header (was only shown in examples) and support for q parameter. Describe using .xml and .json extensions to select return format for testing from browser (where setting accept header is a problem). Document 406 error code return. Document 415 error code return and acceptable content types. Previously only doc was in examples. Set up tests for 406 and 415 error codes.

def init_severity(db, cl, nodeid, newvalues):
    """Make sure severity is set on new issues"""
    if 'severity' in newvalues and newvalues['severity']:
        return

    normal = db.severity.lookup('normal')
    newvalues['severity'] = normal

def init(db):
    db.issue.audit('create', init_severity)