diff --git a/n2vc/exceptions.py b/n2vc/exceptions.py
index c8e8793..a663c62 100644
--- a/n2vc/exceptions.py
+++ b/n2vc/exceptions.py
@@ -12,6 +12,7 @@
 #     See the License for the specific language governing permissions and
 #     limitations under the License.
 
+
 class JujuCharmNotFound(Exception):
     """The Charm can't be found or is not readable."""
 
@@ -122,3 +123,19 @@
 
     def __str__(self):
         return '<{}> Invalid certificate: {}'.format(type(self), super().__str__())
+
+
+class K8sException(Exception):
+    """
+    K8s exception
+    """
+
+    def __init__(self, message: str):
+        Exception.__init__(self, message)
+        self._message = message
+
+    def __str__(self):
+        return self._message
+
+    def __repr__(self):
+        return self._message
diff --git a/n2vc/k8s_helm_conn.py b/n2vc/k8s_helm_conn.py
index 2b15d76..f7ff853 100644
--- a/n2vc/k8s_helm_conn.py
+++ b/n2vc/k8s_helm_conn.py
@@ -30,6 +30,7 @@
 from uuid import uuid4
 import random
 from n2vc.k8s_conn import K8sConnector
+from n2vc.exceptions import K8sException
 
 
 class K8sHelmConnector(K8sConnector):
@@ -258,7 +259,7 @@
                 msg = 'Cluster has releases and not force. Cannot reset K8s environment. Cluster uuid: {}'\
                     .format(cluster_uuid)
                 self.error(msg)
-                raise Exception(msg)
+                raise K8sException(msg)
 
         if uninstall_sw:
 
@@ -280,7 +281,6 @@
             else:
                 msg = 'Tiller deployment not found in cluster {}'.format(cluster_uuid)
                 self.error(msg)
-                # raise Exception(msg)
 
             self.debug('namespace for tiller: {}'.format(namespace))
 
@@ -346,7 +346,7 @@
                 version_str = '--version {}'.format(parts[1])
                 kdu_model = parts[0]
 
-        # generate a name for the releas. Then, check if already exists
+        # generate a name for the release. Then, check if already exists
         kdu_instance = None
         while kdu_instance is None:
             kdu_instance = K8sHelmConnector._generate_release_name(kdu_model)
@@ -413,7 +413,7 @@
         if rc != 0:
             msg = 'Error executing command: {}\nOutput: {}'.format(command, output)
             self.error(msg)
-            raise Exception(msg)
+            raise K8sException(msg)
 
         self.debug('Returning kdu_instance {}'.format(kdu_instance))
         return kdu_instance
@@ -534,7 +534,7 @@
         if rc != 0:
             msg = 'Error executing command: {}\nOutput: {}'.format(command, output)
             self.error(msg)
-            raise Exception(msg)
+            raise K8sException(msg)
 
         # return new revision number
         instance = await self.get_instance_info(cluster_uuid=cluster_uuid, kdu_instance=kdu_instance)
@@ -599,7 +599,7 @@
         if rc != 0:
             msg = 'Error executing command: {}\nOutput: {}'.format(command, output)
             self.error(msg)
-            raise Exception(msg)
+            raise K8sException(msg)
 
         # return new revision number
         instance = await self.get_instance_info(cluster_uuid=cluster_uuid, kdu_instance=kdu_instance)
@@ -788,7 +788,7 @@
         def get_random_number():
             r = random.randrange(start=1, stop=99999999)
             s = str(r)
-            s = s.rjust(width=10, fillchar=' ')
+            s = s.rjust(10, '0')
             return s
 
         name = name + get_random_number()
@@ -1004,7 +1004,7 @@
         if not os.path.exists(cluster_dir):
             msg = 'Base cluster dir {} does not exist'.format(cluster_dir)
             self.error(msg)
-            raise Exception(msg)
+            raise K8sException(msg)
 
         # kube dir
         kube_dir = cluster_dir + '/' + '.kube'
@@ -1014,7 +1014,7 @@
         if not os.path.exists(kube_dir):
             msg = 'Kube config dir {} does not exist'.format(kube_dir)
             self.error(msg)
-            raise Exception(msg)
+            raise K8sException(msg)
 
         # helm home dir
         helm_dir = cluster_dir + '/' + '.helm'
@@ -1024,7 +1024,7 @@
         if not os.path.exists(helm_dir):
             msg = 'Helm config dir {} does not exist'.format(helm_dir)
             self.error(msg)
-            raise Exception(msg)
+            raise K8sException(msg)
 
         config_filename = kube_dir + '/config'
         return kube_dir, helm_dir, config_filename, cluster_dir
@@ -1143,4 +1143,4 @@
             msg = 'File {} does not exist'.format(filename)
             if exception_if_not_exists:
                 self.error(msg)
-                raise Exception(msg)
+                raise K8sException(msg)
diff --git a/n2vc/n2vc_juju_conn.py b/n2vc/n2vc_juju_conn.py
index aba88ee..a9f9b76 100644
--- a/n2vc/n2vc_juju_conn.py
+++ b/n2vc/n2vc_juju_conn.py
@@ -266,11 +266,11 @@
 
         if credentials is None:
             raise N2VCBadArgumentsException(message='credentials are mandatory', bad_args=['credentials'])
-        if 'hostname' in credentials:
+        if credentials.get('hostname'):
             hostname = credentials['hostname']
         else:
             raise N2VCBadArgumentsException(message='hostname is mandatory', bad_args=['credentials.hostname'])
-        if 'username' in credentials:
+        if credentials.get('username'):
             username = credentials['username']
         else:
             raise N2VCBadArgumentsException(message='username is mandatory', bad_args=['credentials.username'])