Removed config assertion to enable config-file less config

The config lookup works by first checking for the <SECTION>_<VAR> env
var and then looking for the specified <var> in the [<section>] of the
config file. Checking for a specific section in the configuration then
will only work if there is a configuration file, since sections are not
a defined concept in the environment. The test is also unnecesary since
the following var lookup will fail anyway if it's not present.

lega/utils/amqp.py

@@ -19,8 +19,6 @@ def get_connection(domain, blocking=True):
     heartbeat values are read from the CONF argument.
     So are the SSL options.
     """
-    assert domain in CONF.sections(), "Section not found in config file"
-
     LOG.info(f'Getting a connection to {domain}')
     params = CONF.get_value(domain, 'connection', raw=True)
     LOG.debug(f"Initializing a connection to: {params}")