[mod] check secret_key value when the webapp starts

Before this commit the secret_key is checked as soon as the searx module is imported.

So the documentation, utils/standalone_searx.py have to set SEARX_DEBUG=1

With this commit:
* searx check the secret_key when the webapp is loaded
* after searx loads that the engines.

For reference see searx#2386

searx/__init__.py

@@ -60,7 +60,3 @@
     settings['server']['secret_key'] = environ['SEARX_SECRET']
 if 'SEARX_BIND_ADDRESS' in environ:
     settings['server']['bind_address'] = environ['SEARX_BIND_ADDRESS']
-
-if not searx_debug and settings['server']['secret_key'] == 'ultrasecretkey':
-    logger.error('server.secret_key is not changed. Please use something else instead of ultrasecretkey.')
-    exit(1)

searx/webapp.py

@@ -128,11 +128,6 @@
 # see run() at the end of this file : searx_debug activates the reload feature.
 werkzeug_reloader = flask_run_development or (searx_debug and __name__ == "__main__")
 
-# initialize the engines except on the first run of the werkzeug server.
-if not werkzeug_reloader\
-   or (werkzeug_reloader and os.environ.get("WERKZEUG_RUN_MAIN") == "true"):
-    initialize()
-
 babel = Babel(app)
 
 rtl_locales = ['ar', 'arc', 'bcc', 'bqi', 'ckb', 'dv', 'fa', 'fa_IR', 'glk', 'he',
@@ -1135,9 +1130,37 @@ def __call__(self, environ, start_response):
         return self.app(environ, start_response)
 
 
+class InitializeApplication:
+    '''Check settings['server']['secret_key'] when the application is started
+    Allow to import searx.webapp without issue.
+    '''
+
+    def __init__(self, app):
+        self.app = app
+
+        # check secret_key
+        if not searx_debug and settings['server']['secret_key'] == 'ultrasecretkey':
+            logger.error('server.secret_key is not changed. Please use something else instead of ultrasecretkey.')
+            exit(1)
+
+        # initialize the engines except on the first run of the werkzeug server.
+        if not werkzeug_reloader\
+           or (werkzeug_reloader and os.environ.get("WERKZEUG_RUN_MAIN") == "true"):
+            initialize()
+
+    def __call__(self, environ, start_response):
+        return self.app(environ, start_response)
+
+
+# uwsgi application
 application = app
+
 # patch app to handle non root url-s behind proxy & wsgi
 app.wsgi_app = ReverseProxyPathFix(ProxyFix(application.wsgi_app))
 
+# initiliaze the webapp when it is started not loaded
+app.wsgi_app = InitializeApplication(app.wsgi_app)
+
+
 if __name__ == "__main__":
     run()

utils/standalone_searx.py

@@ -15,7 +15,7 @@
 
 .. code::  bash
 
-    $ SEARX_DEBUG=1 python3 utils/standalone_searx.py rain
+    $ python3 utils/standalone_searx.py rain
 
 Example to run it from python: