Started from scratch and failed

Issue with register_blueprint

ref-test/app/config.py

@@ -0,0 +1,44 @@
+import os
+from dotenv import load_dotenv
+load_dotenv()
+
+class Config(object):
+    APP_HOST = '0.0.0.0'
+    DEBUG = False
+    TESTING = False
+    SECRET_KEY = os.getenv('SECRET_KEY')
+    SERVER_NAME = os.getenv('SERVER_NAME')
+    SESSION_COOKIE_SECURE = True
+    SQLALCHEMY_DATABASE_URI = 'sqlite:///data/database.db'
+    SQLALCHEMY_TRACK_MODIFICATIONS = False
+
+    MAIL_SERVER = os.getenv("MAIL_SERVER")
+    MAIL_PORT = int(os.getenv("MAIL_PORT"))
+    MAIL_USE_TLS = False
+    MAIL_USE_SSL = False
+    MAIL_DEBUG = False
+    MAIL_USERNAME = os.getenv("MAIL_USERNAME")
+    MAIL_PASSWORD = os.getenv("MAIL_PASSWORD")
+    MAIL_DEFAULT_SENDER = os.getenv("MAIL_DEFAULT_SENDER")
+    MAIL_MAX_EMAILS = int(os.getenv("MAIL_MAX_EMAILS"))
+    MAIL_SUPPRESS_SEND = False
+    MAIL_ASCII_ATTACHMENTS = bool(os.getenv("MAIL_ASCII_ATTACHMENTS"))
+    DATA_FILE_DIRECTORY = os.getenv("DATA_FILE_DIRECTORY")
+
+class ProductionConfig(Config):
+    pass
+
+class DevelopmentConfig(Config):
+    APP_HOST = '127.0.0.1'
+    DEBUG = True
+    SESSION_COOKIE_SECURE = False
+    MAIL_SERVER = 'localhost'
+    MAIL_DEBUG = True
+    MAIL_SUPPRESS_SEND = False
+
+class TestingConfig(DevelopmentConfig):
+    TESTING = True
+    SESSION_COOKIE_SECURE = False
+    MAIL_SERVER = os.getenv("MAIL_SERVER")
+    MAIL_DEBUG = True
+    MAIL_SUPPRESS_SEND = False