Fix SyntaxWarning for 'is not' with literals

On Python 3.8 there was a change: "The compiler now produces a SyntaxWarning when identity checks (is and is not) are used with certain types of literals (e.g. strings, numbers)."
More info here: https://adamj.eu/tech/2020/01/21/why-does-python-3-8-syntaxwarning-for-is-literal/
Replaced the 'is not' with '!='

KubiScan.py

@@ -281,7 +281,7 @@ def print_pods_with_access_secret_via_volumes(namespace=None):
                             #mount_info += 'Mounted path: {0}\nSecret name: {1}\nVolume name: {2}\n'.format(volume_mount.mount_path, volume.secret.secret_name, volume.name)
                             mount_info += '{2}. Mounted path: {0}\n   Secret name: {1}\n'.format(volume_mount.mount_path, volume.secret.secret_name, secrets_num)
                             secrets_num += 1
-                if mount_info is not '':
+                if mount_info != '':
                     t.add_row([pod.metadata.name, pod.metadata.namespace, container.name, mount_info])
 
     print_table_aligned_left(t)
@@ -301,7 +301,7 @@ def print_pods_with_access_secret_via_environment(namespace=None):
                     if env.value_from is not None and env.value_from.secret_key_ref is not None:
                         mount_info += '{2}. Environemnt variable name: {0}\n   Secret name: {1}\n'.format(env.name, env.value_from.secret_key_ref.name, secrets_num)
                         secrets_num += 1
-                if mount_info is not '':
+                if mount_info != '':
                     t.add_row([pod.metadata.name, pod.metadata.namespace, container.name, mount_info])
 
     print_table_aligned_left(t)