### Description

When Kamailio starts up with app_python3 enabled, multiple threading exceptions appear in the log after forking. The same setup previously using app_python2 exhibits no such errors.

### Expected behavior

When Kamailio starts up with app_python3 enabled, everything is successful.

#### Actual observed behavior

When Kamailio starts up with app_python3 enabled, exceptions in the Python interpreter are logged.

#### Debugging Data

#### Log Messages

[dump.log](https://github.com/kamailio/kamailio/files/3027162/dump.log)

#### SIP Traffic

N/A

### Possible Solutions

The errors may or may not be benign (and thus safe to ignore), routing still appear to work.

### Additional Information

* **Kamailio Version** - output of `kamailio -v`

``` version: kamailio 5.2.2 (x86_64/linux) flags: STATS: Off, USE_TCP, USE_TLS, USE_SCTP, TLS_HOOKS, USE_RAW_SOCKS, DISABLE_NAGLE, USE_MCAST, DNS_IP_HACK, SHM_MEM, SHM_MMAP, PKG_MALLOC, Q_MALLOC, F_MALLOC, TLSF_MALLOC, DBG_SR_MEMORY, USE_FUTEX, FAST_LOCK-ADAPTIVE_WAIT, USE_DNS_CACHE, USE_DNS_FAILOVER, USE_NAPTR, USE_DST_BLACKLIST, HAVE_RESOLV_RES ADAPTIVE_WAIT_LOOPS=1024, MAX_RECV_BUFFER_SIZE 262144 MAX_URI_SIZE 1024, BUF_SIZE 65535, DEFAULT PKG_SIZE 8MB poll method support: poll, epoll_lt, epoll_et, sigio_rt, select. id: unknown compiled with gcc 6.3.0 ```

* **Operating System**:

Debian GNU/Linux 9 (stretch)

``` Linux 4e0ff3e84062 4.15.0-46-generic #49-Ubuntu SMP Wed Feb 6 09:33:07 UTC 2019 x86_64 GNU/Linux ```