docs: def check_env(self, envar, value):
          '''ensure that variable envar is set to some value, 
             otherwise exit on error.
          
             Parameters
             ==========
             envar: the environment variable name
             value: the setting that shouldn't be None
          '''
          if value is None:
              bot.error('You must export %s to use Discourse' % envar)
              print('https://vsoch.github.io/helpme/helper-discourse')
              sys.exit(1)