problems encountered
File “/opt/ros/melodic/bin/roscore”, line 37, in
from roslaunch.nodeprocess import DEFAULT_TIMEOUT_SIGINT, DEFAULT_TIMEOUT_SIGTERM
File “/opt/ros/melodic/lib/python2.7/dist-packages/roslaunch/init.py”, line 52, in
from . import param_dump as roslaunch_param_dump
File “/opt/ros/melodic/lib/python2.7/dist-packages/roslaunch/param_dump.py”, line 40, in
import roslaunch.config
File “/opt/ros/melodic/lib/python2.7/dist-packages/roslaunch/config.py”, line 45, in
import rospkg.distro
File “/opt/ros/melodic/lib/python2.7/dist-packages/rospkg/distro.py”, line 44, in
import yaml
File “/opt/ros/melodic/lib/python2.7/dist-packages/yaml/init.py”, line 8, in
from loader import *
File “/opt/ros/melodic/lib/python2.7/dist-packages/yaml/loader.py”, line 4, in
from reader import *
File “/opt/ros/melodic/lib/python2.7/dist-packages/y