Various CI fixes

.travis.yml

@@ -1,5 +1,9 @@
+dist: bionic
 sudo: false
 language: python
+before_install:
+  # for rpm-py-installer
+  - sudo apt-get install -y rpm
 install: pip install tox
 matrix:
   include:

pubtools/pulplib/_impl/model/common.py

@@ -20,8 +20,7 @@ class DetachedException(Exception):
 
 
 class InvalidDataException(Exception):
-    """Raised if raw Pulp data appears to be invalid (i.e. not matching expected schema).
-    """
+    """Raised if raw Pulp data appears to be invalid (i.e. not matching expected schema)."""
 
 
 class PulpObject(object):

tests/model/assertions.py

@@ -46,9 +46,13 @@ def assert_model_fields(model_object):
         if value is not None:
             # These tests only valid on non-None value.
 
-            assert isinstance(value, field.type), (
-                "%s.%s should be a %s but is not: %s"
-                % (klass.__name__, field.name, field.type.__name__, model_object)
+            assert isinstance(
+                value, field.type
+            ), "%s.%s should be a %s but is not: %s" % (
+                klass.__name__,
+                field.name,
+                field.type.__name__,
+                model_object,
             )
 
             if field.type is list: