Fix CI: Raise specific exception.

Do comparison with !=.

src/main/python/ddadevops/release_mixin.py

@@ -1,5 +1,5 @@
 from typing import Optional
-from pybuilder.core import Project 
+from pybuilder.core import Project
 from src.main.python.ddadevops.devops_build import DevopsBuild
 from src.main.python.ddadevops.infrastructure.release_mixin import ReleaseRepository, ReleaseTypeRepository, VersionRepository, GitApi, EnvironmentApi
 from src.main.python.ddadevops.application import PrepareReleaseService, TagAndPushReleaseService
@@ -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(
@@ -38,8 +38,8 @@ 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)
         else: