Centos7 python 3.7

[sam-github]

Installs python3 in /opt/python-3.7/bin, as python3:

        % /opt/python-3.7/bin/python3 --version
        Python 3.7.3

[sam-github]

@mhdawson LGTY?

@rvagg I don't know state of python3 on ARM, if you need it build because packages don't exist, this will do it.

/to @cclauss @nodejs/python

Also, I'm not sure who is working on updating python support, but note carefully the location of the python3. I'm not sure, is it unreasonably conservative? I could set the prefix to /usr/local to have it in the default path, but that would force there to be only one python3 on the system -- maybe that's OK, even desireable?

[sam-github]

FTR:

build/ansible (centos7-python-3.7 % u=) % ssh test-osuosl-centos7-ppc64_le-1 /opt/python-3.7/bin/python3 --version                                                           
Python 3.7.3
build/ansible (centos7-python-3.7 % u=) % ssh test-osuosl-centos7-ppc64_le-2 /opt/python-3.7/bin/python3 --version
bash: /opt/python-3.7/bin/python3: No such file or directory
build/ansible (centos7-python-3.7 % u=) % ssh test-osuosl-centos7-ppc64_le-1 ls /opt/python-3.7/bin
2to3
2to3-3.7
idle3
idle3.7
pydoc3
pydoc3.7
python3
python3.7
python3.7-config
python3.7m
python3.7m-config
python3-config
pyvenv
pyvenv-3.7

Once we decide on where python should be, I can update this PR, and apply it to the second centos7-ppc machine.

[cclauss]

This is great work! Thanks for doing it. I would prefer if the path to python2 and the path to python3 were the same. That is how it is done on most current distros (if they still ship legacy Python).

[sam-github]

They can't literally be the same paths, I don't think compiling something and installing it into /usr is a good idea, specifically because that is where distros put packages. I can put it in /usr/local, though, it will be in the default PATH, and its where locally installed packages usually go. I'll redo this PR.

[mhdawson]

LGTM

[rvagg]

on arm64 centos7 python34.aarch64 and python36.aarch64 are available, if we need 37 then I guess we need to go this route too

[thefourtheye]

This is great work @sam-github. Thanks a lot. I am also okay with this patch if the default installation location is /usr/local. We wouldn't want to add the path of the new python to PATH variable in our scripts.

[sam-github]

I think this is landable, can I get a re-approval, please?

@mhdawson you'll need to do the release machine, see below.

build/ansible (centos7-python-3.7 *% u=) % parallel-ssh -h ../hosts/osuosl-centos7-ppc64_le -i python3 -m pip --version                                                      
[1] 13:42:43 [FAILURE] release-osuosl-centos7-ppc64_le-1 Exited with error code 255
Stderr: ssh: Could not resolve hostname release-osuosl-centos7-ppc64_le-1: Temporary failure in name resolution                                                              
[2] 13:42:44 [SUCCESS] test-osuosl-centos7-ppc64_le-2
pip 19.0.3 from /usr/local/lib/python3.7/site-packages/pip (python 3.7)
[3] 13:42:45 [SUCCESS] test-osuosl-centos7-ppc64_le-1
pip 19.0.3 from /usr/local/lib/python3.7/site-packages/pip (python 3.7)
build/ansible (centos7-python-3.7 *% u=) % parallel-ssh -h ../hosts/osuosl-centos7-ppc64_le -i python3 --version       
[1] 13:42:54 [FAILURE] release-osuosl-centos7-ppc64_le-1 Exited with error code 255
Stderr: ssh: Could not resolve hostname release-osuosl-centos7-ppc64_le-1: Temporary failure in name resolution
[2] 13:42:55 [SUCCESS] test-osuosl-centos7-ppc64_le-1
Python 3.7.3
[3] 13:42:55 [SUCCESS] test-osuosl-centos7-ppc64_le-2
Python 3.7.3
build/ansible (centos7-python-3.7 *% u=) % parallel-ssh -h ../hosts/osuosl-centos7-ppc64_le -i which python3    
[1] 13:43:03 [FAILURE] release-osuosl-centos7-ppc64_le-1 Exited with error code 255
Stderr: ssh: Could not resolve hostname release-osuosl-centos7-ppc64_le-1: Temporary failure in name resolution
[2] 13:43:04 [SUCCESS] test-osuosl-centos7-ppc64_le-1
/usr/local/bin/python3
[3] 13:43:04 [SUCCESS] test-osuosl-centos7-ppc64_le-2
/usr/local/bin/python3

[mhdawson]

LGTM, lets do this on the release machine when we talk tomorrow about centos7 next steps

[cclauss]

What is next step here?

[sam-github]

Applying the change to the release machine, and merging.

[sam-github]

Landed in 617b2b6, 4618d48