Hanyuu streams files from disk that are unlocked.

[ameliaikeda]

Files can be edited while Hanyuu is reading from them, causing an Invalid File error.
This can be fixed in one of two ways:

1. Locking files while streaming using fcntl.lockf(filename, fcntl.LOCK_EX)
2. Locking files before reading files into RAM (such as a dictionary somewhere containing the open file object like deque(_tmp_files)), again using fcntl.lockf(filename, fcntl.LOCK_EX)
   Option 2 can be implemented without a lock, but it causes a race condition to appear if a file is written to just as/while hanyuu is reading

[Wessie]

We should use option 2 most likely. A combination of lock, read into RAM, release lock.