Rename management command email-mirror to email_mirror.

All other zulip management command names have underscores, so
rename email-mirror to email_mirror.

This will also make it possible to import this module, which will
help in writing tests for it.

puppet/zulip/files/cron.d/email-mirror

@@ -1,3 +1,3 @@
 MAILTO=root
 
-* * * * *   zulip cd /home/zulip/deployments/current && python manage.py email-mirror
+* * * * *   zulip cd /home/zulip/deployments/current && python manage.py email_mirror

puppet/zulip/files/postfix/master.cf

@@ -111,4 +111,4 @@ mailman   unix  -       n       n       -       -       pipe
   flags=FR user=list argv=/usr/lib/mailman/bin/postfix-to-mailman.py
   ${nexthop} ${user}
 zulip unix  -       n       n       -       -       pipe
-  flags= user=zulip argv=/home/zulip/deployments/current/manage.py email-mirror ${original_recipient}
+  flags= user=zulip argv=/home/zulip/deployments/current/manage.py email_mirror ${original_recipient}

zerver/management/commands/email-mirror.py → zerver/management/commands/email_mirror.py

@@ -29,7 +29,7 @@
      environment variable.
 
      In Postfix, you can express that via an /etc/aliases entry like this:
-         |/usr/bin/env python /home/zulip/deployments/current/manage.py email-mirror
+         |/usr/bin/env python /home/zulip/deployments/current/manage.py email_mirror
 """
 
 

zproject/prod_settings_template.py

@@ -222,7 +222,7 @@
 # form username+%[email protected] (which is what you will set as
 # EMAIL_GATEWAY_PATTERN); your email provider should deliver those
 # emails to the [email protected] inbox.  Then you run in a cron
-# job `./manage.py email-mirror` (see puppet/zulip/files/cron.d/email-mirror),
+# job `./manage.py email_mirror` (see puppet/zulip/files/cron.d/email-mirror),
 # which will check that inbox and batch-process any new messages.
 #
 # You will need to configure authentication for the email mirror

zproject/settings.py

@@ -796,7 +796,7 @@ def get_secret(key):
     ("WORKER_LOG_PATH", "/var/log/zulip/workers.log"),
     ("PERSISTENT_QUEUE_FILENAME", "/home/zulip/tornado/event_queues.pickle"),
     ("JSON_PERSISTENT_QUEUE_FILENAME", "/home/zulip/tornado/event_queues.json"),
-    ("EMAIL_MIRROR_LOG_PATH", "/var/log/zulip/email-mirror.log"),
+    ("EMAIL_MIRROR_LOG_PATH", "/var/log/zulip/email_mirror.log"),
     ("EMAIL_DELIVERER_LOG_PATH", "/var/log/zulip/email-deliverer.log"),
     ("LDAP_SYNC_LOG_PATH", "/var/log/zulip/sync_ldap_user_data.log"),
     ("QUEUE_ERROR_DIR", "/var/log/zulip/queue_error"),