SNMP sensor

[fabaff]

Description:
A simple SNMP sensor.

Related issue (if applicable): fixes #

Pull request in home-assistant.io with documentation (if applicable): home-assistant/home-assistant.io#538

Example entry for configuration.yaml (if applicable):

sensor:
  platform: snmp
  name: Load
  host: 192.168.1.1
  community: public
  baseoid: 1.3.6.1.4.1.2021.10.1.3.1

Checklist:

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated in home-assistant.io

If code communicates with devices:

• Local tests with tox run successfully. Your PR cannot be merged unless tests pass
• New dependencies have been added to the REQUIREMENTS variable (example).
• New dependencies are only imported inside functions that use them (example).
• New dependencies have been added to requirements_all.txt by running script/gen_requirements_all.py.
• New files were added to .coveragerc.

If the code does not interact with devices:

• Local tests with tox run successfully. Your PR cannot be merged unless tests pass
• Tests have been added to verify that the new code works.

[rmkraus]

Looks fine to me.

[balloob]

Why can the user pick a unit of measurement ?

Also, we have a constant for that in homeassistant.const.

[fabaff]

Why can the user pick a unit of measurement ?

Because certain nodes inside the tree are delivered without unit of measurement. Others are. Anyway, in a lot of cases it will be necessary to use a template sensor for the conversion in a more human readable form as long that the template support for this sensor is missing.

Also, we have a constant for that in homeassistant.const.

Thanks, was only checking CONF* and not ATTR*.

[balloob]

For future reference, we have cv.string that is slightly better than this.

[balloob]

Looks good! 🐬