fix: what bandit and the remaining lint rules found

- Long lines are wrapped: the get_environment awk command is split into
  adjacent string literals, the rollback message and the system mixin's
  docstring are wrapped; the command and the text are unchanged.
- The two except Exception: pass (the snmpd community in get_snmp_config,
  the network VLANs in get_ssids) now log at debug level (B110), so a
  swallowed failure leaves a trace.
- tests: raise ... from exc, unused loop variable.

tests/unit/test_driver.py

@@ -911,7 +911,7 @@ class TestGetRouteTo:
 
     def test_required_keys(self, driver):
         driver._send_command = lambda cmd, **kw: IP_ROUTE_SHOW
-        for prefix, routes in driver.get_route_to().items():
+        for _prefix, routes in driver.get_route_to().items():
             for route in routes:
                 assert set(route.keys()) >= {
                     "protocol",

tests/unit/test_ssh_host_key.py

@@ -76,7 +76,7 @@ def test_a_changed_key_is_refused():
         try:
             raise paramiko.BadHostKeyException("10.0.0.8", SERVER_KEY, OTHER_KEY)
         except paramiko.SSHException as exc:  # what netmiko does with it
-            raise NetmikoTimeoutException(f"A paramiko SSHException occurred: {exc}")
+            raise NetmikoTimeoutException(f"A paramiko SSHException occurred: {exc}") from exc
 
     driver = _driver(seen, SshHostKey.of(OTHER_KEY))
     with patch(HANDLER, side_effect=refuse):