px4-dev: Try to move to Python 3

[julianoes]

This goes with PX4/PX4-Autopilot#12809.

[TSC21]

This will become problematic for the ROS containers.

[julianoes]

So how can we get ROS to Python 3? It's 2019...

[lamping7]

So how can we get ROS to Python 3? It's 2019...

You can't (without a major effort). Just because it's EOL, doesn't mean it's obsolete.

[julianoes]

Alright but as @dagar suggested we can probably have Python 2 dependencies on higher level containers for ROS.

[cclauss]

In this repo, these Python 3 syntax errors should be fixed:
flake8 testing of https://github.com/PX4/containers on Python 3.7.1

$ flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics

./docker/ros-indigo/sitl-testing/scripts/testing/export_charts.py:145:44: E999 SyntaxError: invalid syntax
            print "Exporting chart %s to %s" % (chart["name"], path)
                                           ^
./docker/ros-indigo/mavros/tools/broadcaster.py:46:21: E999 SyntaxError: invalid syntax
            print ":".join("{:02x}".format(ord(c)) for c in buf)
                    ^
2     E999 SyntaxError: invalid syntax
2

E901,E999,F821,F822,F823 are the "showstopper" flake8 issues that can halt the runtime with a SyntaxError, NameError, etc. These 5 are different from most other flake8 issues which are merely "style violations" -- useful for readability but they do not effect runtime safety.

• F821: undefined name name
• F822: undefined name name in __all__
• F823: local variable name referenced before assignment
• E901: SyntaxError or IndentationError
• E999: SyntaxError -- failed to compile a file into an Abstract Syntax Tree

[julianoes]

@cclauss thanks, see: #200.

[cclauss]

Nice! PX4/PX4-Autopilot#13008 Today, there are 100 days until Python 2 end of life.

Just because it's EOL, doesn't mean it's obsolete.

Just because it's EOL means that it is going to become an attack vector for evil doers because the Python Software Foundation and Python Core Team have been very clear that they will not even fix known security vulnerabilities after 1/1/2020..

[TSC21]

@julianoes what about we keep Python2 together with Python3? I mean, instead of replacing, we duplicate the install steps for Python3

[julianoes]

@TSC21 I would like to move to Python 3 as much as possible. Otherwise we'll be stuck with Python 2 forever. I suggest that add whatever Python 2 things are necessary for ROS in the ROS containers.

[TSC21]

@TSC21 I would like to move to Python 3 as much as possible. Otherwise we'll be stuck with Python 2 forever. I suggest that add whatever Python 2 things are necessary for ROS in the ROS containers.

Can we at least keep python-pip and python-setuptools? If not, can you move it to the simulation containers on this PR?

[julianoes]

Can we at least keep python-pip and python-setuptools?

I wouldn't add dependencies that are not used in the same scope. Otherwise the next person will remove them again because it's not clear why they are there.

Feel free to add commits to add what ROS requires.

[TSC21]

Can we at least keep python-pip and python-setuptools?

I wouldn't add dependencies that are not used in the same scope. Otherwise the next person will remove them again because it's not clear why they are there.

Feel free to add commits to add what ROS requires.

The problem is not just ROS: http://ci.px4.io:8080/blue/organizations/jenkins/PX4%2Fcontainers/detail/PR-199/2/pipeline/#step-104-log-33

[julianoes]

Alright, I'll fix it.

Yes, it's a chicken and egg problem. It also requires PX4/PX4-Autopilot#12809.

[TSC21]

@julianoes instead of mutually excluding Python 2 and 3, let's for now keep Python 2 in the container and install Python 3 in parallel. Does that work for you?

[cclauss]

With 44 days left until Python 2 end of life, why not put Python 2 in the trash and install Python 3 everywhere? Python 3 has been in existence for 13+ years.

[TSC21]

With 44 days left until Python 2 end of life, why not put Python 2 in the trash and install Python 3 everywhere? Python 3 has been in existence for 13+ years.

Because we still have a "problem" called ROS ;)

[TSC21]

@julianoes I say we give this a shot and let it go through, so we can solve the chicken and egg problem. Then we address whatever it's required. Let's unblock this - can you please set the master branch for the Jenkins stages and bring this in? Thanks!

[julianoes]

@TSC21 I think we need to release this and create a tag and then reference to this, right?

[cclauss]

I thought the Python 3 thing was already solved in ROS... apt-get install python3-rospkg python3-rospkg-modules python3-catkin-pkg python3-catkin-pkg-modules

http://wiki.ros.org/rospkg
http://wiki.ros.org/catkin_pkg
https://index.ros.org/deps/page/22/name/
https://index.ros.org/deps/page/23/name/

[TSC21]

I thought the Python 3 thing was already solved in ROS... apt-get install python3-rospkg python3-rospkg-modules python3-catkin-pkg python3-catkin-pkg-modules

http://wiki.ros.org/rospkg
http://wiki.ros.org/catkin_pkg
https://index.ros.org/deps/page/22/name/
https://index.ros.org/deps/page/23/name/

Yep, but those are for ROS 2 ;)

[TSC21]

@TSC21 I think we need to release this and create a tag and then reference to this, right?

Yes. Just change the Jenkins stuff and I can do that immediately if you want.

[TSC21]

I am merging this now and tagging it so we can solve PX4/PX4-Autopilot#12809.