Issue 31723: Support for python3 in jenkins_script module

[Leibniz137]

SUMMARY

Make jenkins_script module compatible with python3 by convert bytes to str when necessary
Fixes #31723

ISSUE TYPE

• Bugfix Pull Request

COMPONENT NAME

jenkins_script

ANSIBLE VERSION

ansible 2.4.1.0
  config file = /Users/ng186024/src/cit/td_jenkins_master/ansible/ansible.cfg
  configured module search path = ['/Users/ng186024/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /Users/ng186024/.virtualenvs/jenkins/lib/python3.6/site-packages/ansible
  executable location = /Users/ng186024/.virtualenvs/jenkins/bin/ansible
  python version = 3.6.0 (default, Jan 21 2017, 10:40:54) [GCC 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.42.1)]

ADDITIONAL INFORMATION

In python3, ansible's fetch_url utility function wraps urllib.request.urlopen.
For HTTP and HTTPS URLs, this function returns a http.client.HTTPResponse object slightly modified.
Calling .read() on an HTTPResponse object returns bytes (note the docstring fix).

Here, to_native is used to convert the bytestrings returned by fetch_url into unicode strings.
This is necessary because:

1. Pre python3.6, json.loads requires passing a string, not a bytestring, as its argument
2. In python3 generally, testing if a string is a substring of a bytestring
   using the 'in' operator will raise a TypeError

see:

• https://docs.python.org/3/library/urllib.request.html#urllib.request.urlopen
• https://docs.python.org/3/library/http.client.html#http.client.HTTPResponse.read
• https://docs.python.org/3/library/json.html#json.loads

before:

An exception occurred during task execution. To see the full traceback, use -vvv. The error was: TypeError: a bytes-like object is required, not 'str'
fatal: [sdvl3jenk042 -> localhost]: FAILED! => {"changed": false, "failed": true, "module_stderr": "Traceback (most recent call last):
  File \"/var/folders/g3/rt5fttrd1dx9gxpqhgh903znwg38nv/T/ansible_prohpe7i/ansible_module_jenkins_script.py\", line 196, in <module>
    main()
  File \"/var/folders/g3/rt5fttrd1dx9gxpqhgh903znwg38nv/T/ansible_prohpe7i/ansible_module_jenkins_script.py\", line 187, in main
    if 'Exception:' in result and 'at java.lang.Thread' in result:\nTypeError: a bytes-like object is required, not 'str'
", "module_stdout": "", "msg": "MODULE FAILURE", "rc": 0}

after:

ok: [sdvl3jenk042 -> localhost]

[ansibot]

cc @hogarthj
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[resmo]

code LGTM
shipit

[hogarthj]

shipit