Replace InsecureRequestWarning with standard logs

[ofek]

Motivation

Make the warning granular per request without modifying global interpreter state

Additional Notes

Based on https://urllib3.readthedocs.io/en/latest/user-guide.html#certificate-verification, you set the SSL verification method via the constant's name:

>>> import certifi
>>> import urllib3
>>> http = urllib3.PoolManager(
...     cert_reqs='CERT_REQUIRED',
...     ca_certs=certifi.where())

• https://github.com/urllib3/urllib3/blob/46fc29d5108553a58cc14d28e73443e864be76c2/src/urllib3/connectionpool.py#L985-L994
• https://github.com/urllib3/urllib3/blob/d455be9463b547b4a6efb3b6de52abfe2b62e3e8/src/urllib3/connection.py#L419-L422
• https://github.com/psf/requests/blob/1f7c88880b2fa56947d844202127782a50e871e7/requests/adapters.py#L237

[codecov]

Codecov Report

Merging #7512 into master will decrease coverage by 3.09%.
The diff coverage is n/a.

Impacted Files	Coverage Δ
ssh_check/datadog_checks/ssh_check/__init__.py
teamcity/datadog_checks/teamcity/teamcity.py
haproxy/tests/conftest.py
openstack_controller/tests/common.py
tomcat/datadog_checks/tomcat/__about__.py
envoy/tests/conftest.py
fluentd/tests/test_integration.py
linkerd/datadog_checks/linkerd/metrics.py
mesos_slave/tests/utils.py
...g_checks_base/datadog_checks/base/utils/limiter.py
... and 768 more

[AlexandreYang]

(nit)

Looks like we are repeating a lot of logic like this in test.

Maybe we should have some kind of utils to avoid duplication.

        expected_message = 'An unverified HTTPS request is being made to https://www.google.com'
        for _, level, message in caplog.record_tuples:
            if level == logging.WARNING and message == expected_message:
                break
        else:
            raise AssertionError('Expected WARNING log with message `{}`'.format(expected_message))

[ofek]

good idea, I'll add one in a separate PR after this is merged