Load gunicorn defaults before overriding with app settings

fixes: pulp#4917

CHANGES/4917.feature

@@ -0,0 +1 @@
+Enable the gunicorn applications for pulp-api and pulp-content to load configs from a "gunicorn.conf.py" file.

pulpcore/app/entrypoint.py

@@ -9,7 +9,7 @@
 from django.db import connection
 from django.db.utils import InterfaceError, OperationalError
 from gunicorn.workers.sync import SyncWorker
-from gunicorn.app.base import BaseApplication
+from gunicorn.app.base import Application
 
 from pulpcore.app.apps import pulp_plugin_configs
 
@@ -80,12 +80,22 @@ def run(self):
                 self.api_app_status.delete()
 
 
-class PulpcoreApiApplication(BaseApplication):
+class PulpcoreApiApplication(Application):
     def __init__(self, options):
         self.options = options or {}
         super().__init__()
 
+    def init(self, *args, **kwargs):
+        """
+        A hook for setting application-specific configs, which we instead do below in load_config
+        where it's non-overridable.
+        """
+        pass
+
     def load_config(self):
+        # Load default gunicorn configs, including reading from the default config file.
+        super().load_config()
+        # Override with settings that we've specified in the startup script.
         [
             self.cfg.set(key.lower(), value)
             for key, value in self.options.items()

pulpcore/content/entrypoint.py

@@ -1,13 +1,23 @@
 import click
-from gunicorn.app.base import BaseApplication
+from gunicorn.app.base import Application
 
 
-class PulpcoreContentApplication(BaseApplication):
+class PulpcoreContentApplication(Application):
     def __init__(self, options):
         self.options = options or {}
         super().__init__()
 
+    def init(self, *args, **kwargs):
+        """
+        A hook for setting application-specific configs, which we instead do below in load_config
+        where it's non-overridable.
+        """
+        pass
+
     def load_config(self):
+        # Load default gunicorn configs, including reading from the default config file.
+        super().load_config()
+        # Override with settings that we've specified in the startup script.
         [
             self.cfg.set(key.lower(), value)
             for key, value in self.options.items()