remove legacy Python2 components

[RafalSkolasinski]

What this PR does / why we need it:

Remove some obsolete elements relevant only for Python2.

Which issue(s) this PR fixes:

Closes #1438

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

Python 2 compatibility layer removed completely. 

[RafalSkolasinski]

/test
/test integration

[seldondev]

Mon Nov 30 17:35:59 UTC 2020
The logs for [pr-build] [1] will show after the pipeline context has finished.
https://github.com/SeldonIO/seldon-core/blob/gh-pages/jenkins-x/logs/SeldonIO/seldon-core/PR-2724/1.log

impatient try
jx get build logs SeldonIO/seldon-core/PR-2724 --build=1

[seldondev]

Mon Nov 30 17:36:07 UTC 2020
The logs for [lint] [2] will show after the pipeline context has finished.
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jx get build logs SeldonIO/seldon-core/PR-2724 --build=2

[seldondev]

Mon Nov 30 17:36:14 UTC 2020
The logs for [integration] [3] will show after the pipeline context has finished.
https://github.com/SeldonIO/seldon-core/blob/gh-pages/jenkins-x/logs/SeldonIO/seldon-core/PR-2724/3.log

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jx get build logs SeldonIO/seldon-core/PR-2724 --build=3

[axsaucedo]

Nice one
/approve

[seldondev]

Tue Dec 1 12:58:38 UTC 2020
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[seldondev]

Tue Dec 1 12:58:39 UTC 2020
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[seldondev]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: axsaucedo

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[RafalSkolasinski]

/test integration

[seldondev]

Tue Dec 1 13:04:33 UTC 2020
The logs for [pr-build] [6] will show after the pipeline context has finished.
https://github.com/SeldonIO/seldon-core/blob/gh-pages/jenkins-x/logs/SeldonIO/seldon-core/PR-2724/6.log

impatient try
jx get build logs SeldonIO/seldon-core/PR-2724 --build=6

[seldondev]

Tue Dec 1 13:05:00 UTC 2020
The logs for [lint] [8] will show after the pipeline context has finished.
https://github.com/SeldonIO/seldon-core/blob/gh-pages/jenkins-x/logs/SeldonIO/seldon-core/PR-2724/8.log

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jx get build logs SeldonIO/seldon-core/PR-2724 --build=8

[seldondev]

Tue Dec 1 13:05:00 UTC 2020
The logs for [pr-build] [7] will show after the pipeline context has finished.
https://github.com/SeldonIO/seldon-core/blob/gh-pages/jenkins-x/logs/SeldonIO/seldon-core/PR-2724/7.log

impatient try
jx get build logs SeldonIO/seldon-core/PR-2724 --build=7

[seldondev]

Tue Dec 1 13:05:04 UTC 2020
The logs for [integration] [10] will show after the pipeline context has finished.
https://github.com/SeldonIO/seldon-core/blob/gh-pages/jenkins-x/logs/SeldonIO/seldon-core/PR-2724/10.log

impatient try
jx get build logs SeldonIO/seldon-core/PR-2724 --build=10

[seldondev]

Tue Dec 1 13:06:39 UTC 2020
The logs for [lint] [9] will show after the pipeline context has finished.
https://github.com/SeldonIO/seldon-core/blob/gh-pages/jenkins-x/logs/SeldonIO/seldon-core/PR-2724/9.log

impatient try
jx get build logs SeldonIO/seldon-core/PR-2724 --build=9

[RafalSkolasinski]

@axsaucedo integration tests passed, shall we?

comparing to first version I undid modification to grpc component as this one is auto-generated