[ros2doctor] Python exception thrown when following tutorial.

Bug report

Running ros2 doctor --report in a Docker container fails with a Python stack trace

Required Info:

• Operating System:
  • Ubuntu 18.04.3 in ros:eloquent docker image
• Installation type:
  • Docker image, not sure how the docker image itself is built
• Version or commit hash:
  • 0.8.6 (as found by dpkg -S ros2cli, there is no -v flag yet)
• DDS implementation:
  • Fast-RTPS (nothing installed additional to what’s in the docker image)

Steps to reproduce issue

I was following https://index.ros.org/doc/ros2/Tutorials/Getting-Started-With-Ros2doctor/#id6 in said docker image:

ros2 doctor
ros2 doctor --report

Expected behavior

An error information about network configuration

Actual behavior

root@5832e3497fea:~/ros2/dev_ws# ros2 doctor
/opt/ros/eloquent/lib/python3.6/site-packages/ros2doctor/api/format.py: 76: UserWarning: ERROR: No loopback IP address is found.
/opt/ros/eloquent/lib/python3.6/site-packages/ros2doctor/api/format.py: 76: UserWarning: Only loopback IP address is found.
/opt/ros/eloquent/lib/python3.6/site-packages/ros2doctor/api/format.py: 76: UserWarning: No multicast IP address is found.
/opt/ros/eloquent/lib/python3.6/site-packages/ros2doctor/api/format.py: 76: UserWarning: Publisher without subscriber detected on /topic.

1/3 checks failed

Failed modules: network
root@5832e3497fea:~/ros2/dev_ws# ros2 doctor --report

  NETWORK CONFIGURATION
Traceback (most recent call last):
  File "/opt/ros/eloquent/bin/ros2", line 11, in <module>
    load_entry_point('ros2cli==0.8.6', 'console_scripts', 'ros2')()
  File "/opt/ros/eloquent/lib/python3.6/site-packages/ros2cli/cli.py", line 69, in main
    rc = extension.main(parser=parser, args=args)
  File "/opt/ros/eloquent/lib/python3.6/site-packages/ros2doctor/command/doctor.py", line 45, in main
    format_print(report_obj)
  File "/opt/ros/eloquent/lib/python3.6/site-packages/ros2doctor/api/format.py", line 27, in format_print
    padding_num = compute_padding(report.items)
  File "/opt/ros/eloquent/lib/python3.6/site-packages/ros2doctor/api/format.py", line 40, in compute_padding
    check_items = list(zip(*report_items))[0]  # get first elements of tuples
IndexError: list index out of range
root@5832e3497fea:~/ros2/dev_ws#

Additional information

Output of ifconfig, inside the docker container

eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 172.17.0.2  netmask 255.255.0.0  broadcast 172.17.255.255
        ether 02:42:ac:11:00:02  txqueuelen 0  (Ethernet)
        ...

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        loop  txqueuelen 1000  (Local Loopback)
        ...

[LoyVanBeek]

The problem is with python3-ifcfg rather than ros2 doctor maybe, so I proposed a PR there. No change to ros2 doctor is required I think because it already handles errors like this.

With https://github.com/ftao/python-ifcfg/pull/45, the output in the docker container is

root@83317aab73fc:/python-ifcfg/src/ifcfg# ros2 doctor --report
Neither `ifconfig` nor `ip` commands are available, listing network interfaces is likely to fail
/bin/sh: 1: ip: not found

/opt/ros/eloquent/lib/python3.6/site-packages/ros2doctor/api/format.py: 76: UserWarning: Fail to call NetworkReport class functions.

  PLATFORM INFORMATION
system           : Linux
platform info    : Linux-4.15.0-72-generic-x86_64-with-Ubuntu-18.04-bionic
release          : 4.15.0-72-generic
processor        : x86_64

  RMW MIDDLEWARE
middleware name    : rmw_fastrtps_cpp

  ROS 2 INFORMATION
distribution name      : eloquent
distribution type      : ros2
distribution status    : active
release platforms      : {'ubuntu': ['bionic']}

  TOPIC LIST
topic               : none
publisher count     : 0
subscriber count    : 0

Having the error up top is quite clear I think and at least the other info is shown.

[dirk-thomas]

Manually installing net-tools doesn’t seem like a valid fix for this problem. When the user installs the Debian package it should also install necessary dependencies and the user shouldn’t see an exception when invoking ros2 doctor without manually installing other packages.