Generate random session secret if none is supplied

config.py.example

 # Defaults for development ,do not use in production!
 DEBUG = True
 VIDEOPREFIX = 'https://videoag.fsmpi.rwth-aachen.de'
+#SECRET_KEY = 'something random'
 
 DB_SCHEMA = 'db_schema.sql'
 DB_DATA = 'db_example.sql'

server.py

@@ -31,6 +31,8 @@ if not sys.argv[0].endswith('run.py'):
 config.from_pyfile('config.py', silent=True)
 if config['DEBUG']:
 	app.jinja_env.auto_reload = True
+if not config.get('SECRET_KEY', None):
+	config['SECRET_KEY'] = os.urandom(24)
 
 from db import query, searchquery, ldapauth, ldapget, convert_timestamp