Fix CI: Raise specific exception.

Do comparison with !=.

src/main/python/ddadevops/release_mixin.py

@@ -23,7 +23,7 @@ class ReleaseMixin(DevopsBuild):
     def __init__(self, project: Project, config: Optional[dict] = None, release_config: Optional[ReleaseConfig] = None):
         if not release_config:
             if not config:
-                raise Exception("Release parameters could not be set.")
+                raise ValueError("Release parameters could not be set.")
             super().__init__(project, config=config)
             release_mixin_config = config['ReleaseMixin']
             release_config = ReleaseConfig(
@@ -38,7 +38,7 @@ class ReleaseMixin(DevopsBuild):
         git_api = GitApi()
         environment_api = EnvironmentApi()
         env_key = EnvironmentKeys.DDADEVOPS_RELEASE_TYPE.name
-        environment_val_set = environment_api.get(env_key) is not "" and environment_api.get(env_key) is not None
+        environment_val_set = environment_api.get(env_key) != "" and environment_api.get(env_key) is not None
 
         if environment_val_set:
             release_type_repo = ReleaseTypeRepository.from_environment(environment_api)