enable setting SERVER_EMAIL from env, use DEFAULT_FROM_EMAIL for send_mail

From documentation for DEFAULT_FROM_EMAIL:

Default email address to use for various automated correspondence from the site manager(s).
This doesn’t include error messages sent to ADMINS and MANAGERS; for that, see SERVER_EMAIL.

That means it makes sense to make SERVER_EMAIL and DEFAULT_FROM_EMAIL separate settings and
not set one from another.

config.py

@@ -57,8 +57,6 @@ BASE_URL = os.environ.get('BASE_URL', 'http://avatars.linux-kernel.at/avatar/')
 
 LOGIN_REDIRECT_URL = reverse_lazy('profile')
 MAX_LENGTH_EMAIL = 254  # http://stackoverflow.com/questions/386294
-SERVER_EMAIL = 'accounts@mg.linux-kernel.at'
-DEFAULT_FROM_EMAIL = SERVER_EMAIL
 
 MAX_NUM_PHOTOS = 5
 MAX_NUM_UNCONFIRMED_EMAILS = 5
@@ -108,6 +106,7 @@ else:
         }
         EMAIL_BACKEND = 'anymail.backends.mailgun.EmailBackend'  # pragma: no cover
 
+SERVER_EMAIL = os.environ.get('SERVER_EMAIL', 'ivatar@mg.linux-kernel.at')
 DEFAULT_FROM_EMAIL = os.environ.get('DEFAULT_FROM_EMAIL', 'ivatar@mg.linux-kernel.at')
 
 try:

ivatar/ivataraccount/models.py

@@ -31,7 +31,7 @@ from libravatar import libravatar_url
 from ivatar.settings import MAX_LENGTH_EMAIL, logger
 from ivatar.settings import MAX_PIXELS, AVATAR_MAX_SIZE, JPEG_QUALITY
 from ivatar.settings import MAX_LENGTH_URL
-from ivatar.settings import SECURE_BASE_URL, SITE_NAME, SERVER_EMAIL
+from ivatar.settings import SECURE_BASE_URL, SITE_NAME, DEFAULT_FROM_EMAIL
 from .gravatar import get_photo as get_gravatar_photo
 
 
@@ -383,7 +383,7 @@ class UnconfirmedEmail(BaseAccountModel):
         # if settings.DEBUG:
         #    print('DEBUG: %s' % link)
         send_mail(
-            email_subject, email_body, SERVER_EMAIL,
+            email_subject, email_body, DEFAULT_FROM_EMAIL,
             [self.email])
         return True