Add SECRET_KEY configuration.

config.py

@@ -3,3 +3,26 @@ import os
 
 class Config:
     SECRET_KEY = os.environ.get('SECRET_KEY') or 'hard to guess string'
+
+    @staticmethod
+    def init_app(app):
+        pass
+
+
+class DevelopmentConfig(Config):
+    DEBUG = True
+
+
+# class TestingConfig(Config):
+
+
+# class ProductionConfig(Config):
+
+
+config = {
+    'development': DevelopmentConfig,
+    # 'testing': TestingConfig,
+    # 'production': ProductionConfig,
+
+    'default': DevelopmentConfig
+}