`SYS_SOCK_READ_TIMEDOUT` doesnt exist in irods.exception

[mstfdkmn]

I think the SYS_SOCK_READ_TIMEDOUT exception occurs when the server doesn't respond in time during object download/read operations. If this is the case, could we add it to the exception.py file?

[korydraughn]

@d-w-moore Please close if complete.