Require DJANGO_DB_USER and DJANGO_REPLICA_DB_USER

These environment variables are now required.  Previously, the
corresponding Django settings would default to 'gracedb'.

Dockerfile

@@ -81,6 +81,7 @@ RUN mkdir /app/logs /app/project_data
 WORKDIR /app/gracedb_project
 RUN DJANGO_SETTINGS_MODULE=${SETTINGS_MODULE} \
     DJANGO_DB_NAME=fake_name \
+    DJANGO_DB_USER=fake_user \
     DJANGO_DB_PASSWORD=fake_password \
     DJANGO_SECRET_KEY=fake_key \
     DJANGO_PRIMARY_FQDN=fake_fqdn \

config/settings/container/base.py

 # For running a containerized version of the service that gets secrets
 # from environment variables. Builds on base.py settings.
-
 import os
 from django.core.exceptions import ImproperlyConfigured
 from ..base import *
 
 # Get required variables from environment variables ---------------------------
+# Get database user from environment and check
+db_user = os.environ.get('DJANGO_DB_USER', None)
+if db_user is None:
+    raise ImproperlyConfigured('Could not get database user from envvars.')
+
 # Get database password from environment and check
 db_password = os.environ.get('DJANGO_DB_PASSWORD', None)
 if db_password is None:
@@ -72,7 +76,7 @@ DATABASES = {
     'default' : {
         'NAME': db_name,
         'ENGINE': 'django.db.backends.mysql',
-        'USER': os.environ.get('DJANGO_DB_USER', 'gracedb'),
+        'USER': db_user,
         'PASSWORD': db_password,
         'HOST': os.environ.get('DJANGO_DB_HOST', ''),
         'PORT': os.environ.get('DJANGO_DB_PORT', ''),

config/settings/container/dev.py

 # Settings for a test/dev GraceDB instance running in a container
-#import socket
 from .base import *
 
 CONFIG_NAME = "TEST"

config/settings/container/production.py

 # Settings for a production GraceDB instance running in a container
-import copy
 from django.core.exceptions import ImproperlyConfigured
 from .base import *
 
@@ -35,6 +34,10 @@ else:
     if replica_db_name is None:
         raise ImproperlyConfigured('Could not get replica database name from '
             'envvars.')
+    replica_db_user = os.environ.get('DJANGO_REPLICA_DB_USER', None)
+    if replica_db_user is None:
+        raise ImproperlyConfigured('Could not get replica database user '
+            'from envvars.')
     replica_db_password = os.environ.get('DJANGO_REPLICA_DB_PASSWORD', None)
     if replica_db_password is None:
         raise ImproperlyConfigured('Could not get replica database password '
@@ -44,7 +47,7 @@ else:
     read_replica = {
         'NAME': replica_db_name,
         'ENGINE': 'django.db.backends.mysql',
-        'USER': os.environ.get('DJANGO_REPLICA_DB_USER', 'gracedb'),
+        'USER': replica_db_user,
         'PASSWORD': replica_db_password,
         'HOST': os.environ.get('DJANGO_REPLICA_DB_HOST', ''),
         'PORT': os.environ.get('DJANGO_REPLICA_DB_PORT', ''),