tools: frr-reload.py must use python2

[mjstapp]

Use python2 explicitly in frr-reload.py - on ubuntu 20 for example, "python" is now python3.

[LabN-CI]

💚 Basic BGPD CI results: SUCCESS, 0 tests failed

Results table

_	_
Result	SUCCESS git merge/6434 393a003
Date	05/20/2020
Start	16:25:28
Finish	16:51:13
Run-Time	25:45
Total	1815
Pass	1815
Fail	0
Valgrind-Errors	0
Valgrind-Loss	0
Details	vncregress-2020-05-20-16:25:28.txt
Log	autoscript-2020-05-20-16:26:25.log.bz2
Memory	464 444 428

For details, please contact louberger

[NetDEF-CI]

Continuous Integration Result: SUCCESSFUL

Congratulations, this patch passed basic tests

Tested-by: NetDEF / OpenSourceRouting.org CI System

CI System Testrun URL: https://ci1.netdef.org/browse/FRR-FRRPULLREQ-12358/

This is a comment from an automated CI system.
For questions and feedback in regards to this CI system, please feel free to email
Martin Winter - mwinter (at) opensourcerouting.org.

Warnings Generated during build:

Debian 10 amd64 build: Successful with additional warnings

Debian Package lintian failed for Debian 10 amd64 build:
(see full package build log at https://ci1.netdef.org/browse/FRR-FRRPULLREQ-12358/artifact/DEB10BUILD/ErrorLog/log_lintian.txt)

W: frr source: pkg-js-tools-test-is-missing
W: frr source: newer-standards-version 4.4.1 (current is 4.3.0)
W: frr source: pkg-js-tools-test-is-missing
W: frr source: newer-standards-version 4.4.1 (current is 4.3.0)
W: frr-doc: changelog-file-missing-explicit-entry 6.0-2 -> 7.5-dev-20200520-02-g393a00386-0 (missing) -> 7.5-dev-20200520-02-g393a00386-0~deb10u1
W: frr-pythontools: changelog-file-missing-explicit-entry 6.0-2 -> 7.5-dev-20200520-02-g393a00386-0 (missing) -> 7.5-dev-20200520-02-g393a00386-0~deb10u1
W: frr: changelog-file-missing-explicit-entry 6.0-2 -> 7.5-dev-20200520-02-g393a00386-0 (missing) -> 7.5-dev-20200520-02-g393a00386-0~deb10u1
W: frr-snmp: changelog-file-missing-explicit-entry 6.0-2 -> 7.5-dev-20200520-02-g393a00386-0 (missing) -> 7.5-dev-20200520-02-g393a00386-0~deb10u1
W: frr-rpki-rtrlib: changelog-file-missing-explicit-entry 6.0-2 -> 7.5-dev-20200520-02-g393a00386-0 (missing) -> 7.5-dev-20200520-02-g393a00386-0~deb10u1

[donaldsharp]

What issues are you seeing with python 3? I would like to understand a bit better before throwing in the towel and putting in a hard dependancy on python2 especially since python2 is deprecated.

[mjstapp]

I saw cli processing failures running a couple of the topotests that use frr-reload to make config changes; I'm using an ubuntu20 vm, where 'python' is now python3. I guess I saw this as a temporary way to avoid blocking everyone on newer environments, offering a window to resolve the issue.

What issues are you seeing with python 3? I would like to understand a bit better before throwing in the towel and putting in a hard dependancy on python2 especially since python2 is deprecated.

[donaldsharp]

This patch is a hard nack from me. frr-reload.py has code in it that attempts to bridge the gap between people using 2 or 3. If people are using 3 and it is failing then we should fix that not downgrade it to a version of python that is completely out of support. If there are specific test cases that are failing using frr-reload.py in topotests then I would like to understand what ones they are so it can be fixed appropriately.

[donaldsharp]

python2 is deprecated and I will not advocate intentionally turning backwards here. We must move forward by identifying and fixing issues seen in python3 running this script.

[qlyoung]

Yeah, let's either see what the bugs are and fix them specifically, or (my preference) go the reverse direction and force python 3.

[donaldsharp]

I agree w/ Quentin I would prefer forcing python3 as the answer here as well.

[mjstapp]

Fair enough