Add cloudwatch Target

[uritau]

What does this do?

This PR adds a Cloudwatch Target to simplify the usage of Cloudwatch datasource.
.

Why is it a good idea?

This allows users to use Cloudwatch datasource with specific target (limiting and simplifiying the call) and doesn't interferes with anything else on grafanalib.

Questions

• There is no test for this set, I will start working on it ASAP.
• I feel that hardcoding here the validNamespaces and validRegions is not the best approach, but I haven't been able to find any AWS API to gather this information without registering in AWS :( so that's why exists the checkParams, with false this will not be updated.

Usage example

from grafanalib.core import *
from grafanalib.cloudwatch import CloudwatchTarget


dashboard = Dashboard(
    title="Clowdwatch Stats",
    rows=[
        Row(panels=[
            Graph(
                title="Cloudwatch ASG",
                dataSource='Cloudwatch',
                targets=[
                    CloudwatchTarget(
                        dimensions={
                            "AutoScalingGroupName": "frontend-asg-name",
                        },
                        metricName="CPUUtilization",
                        namespace="AWS/EC2",
                        region="eu-west-1",
                        statistics=["Average"],
                    ),
                ],
                yAxes=[
                    YAxis(format=PERCENT_UNIT_FORMAT),
                    YAxis(format=SHORT_FORMAT),
                ],
            ),
        ]),
    ],
).auto_panel_ids()

[atreyd]

When can we expect this feature to be merged. I am looking forward to use this feature for creating the AWS cloudwatch dashboards using grafanalib.

[uritau]

Updating to new junit_family, related with:
pytest-dev/pytest#6179

[dholbach]

Can we make this a separate PR maybe? It definitely makes sense:

.tox/py37/lib/python3.7/site-packages/_pytest/junitxml.py:436
  /home/daniel/dev/grafanalib/.tox/py37/lib/python3.7/site-packages/_pytest/junitxml.py:436: PytestDeprecationWarning: The 'junit_family' default value will change to 'xunit2' in pytest 6.0.
  Add 'junit_family=xunit1' to your pytest.ini file to keep the current format in future versions of pytest and silence this warning.
    _issue_warning_captured(deprecated.JUNIT_XML_DEFAULT_FAMILY, config.hook, 2)

[dholbach]

Moved it to #236

[dholbach]

Would it make sense to use something like https://stackoverflow.com/a/38451512 here?

[dholbach]

Just a quick PSA from me:

1. we're hanging out in #grafanalib on Slack
2. we're planning a contributors meeting soon: here's the link to the doodle to find a good time - be sure to pick your timezone before submitting (preliminary agenda)

We'd love to see you there.

[matthewmrichter]

Typo here but it's inconsequential

[matthewmrichter]

@uritau - Please review the circlci tests, it looks like you'll need to make some formatting changes to pass the tests.

[matthewmrichter]

Please check CircleCI

[kopatsy]

dict.update returns None (https://docs.python.org/3/library/stdtypes.html#dict.update) which means that the target json ends up being null.

[dholbach]

Thanks again for your PR. It's been a while since we reviewed this. We'll close the PR for now as grafanalib mainline has already moved on a bit. Please reopen the PR if you (or anyone else) wants to move this work forward again. We're also happy to chat with you on Slack if you have any questions.