Investigate memory leak

[rhysyngsun]

Steps to Reproduce

When running the subscribe_all_users_to_channel command we saw memory use snowball and not recover. There is probably a memory leak in one of these areas:

• reddit api call to add subscriber
• reindexing task that triggers when user subscribes

Expected Behavior

No memory leak

[rhysyngsun]

We also saw a similar memory leak when sending frontpage emails, so it's probable these are the same leak.