Commonpy

Changes in this release:

* `data_utils.flattened` now outputs `[]` as the value of dict or mapping keys whose original values are an empty sequence (e.g., when the value of a dict key is `[]`). Previously, it would output `None` as the value, which was an unexpected transformation of the input.

Bug fixes in this release:

* Fixed a bug in `data_utils.flattened` that caused it to ignore the `separator` argument in some cases.
* Fixed a missing import of `freezegun` in `requirements-dev.txt`.
* Pin the imported version of regex 2022.3.2, because more recent versions cause calls to `dateparser` to encounter an error ("regex._regex_core.error: bad escape \d at position 7").

The main functional change in this release is that error objects returned by `net(...)` will have error message bodies returned by network services, where possible.

Internally, there has been some refactoring of the Makefile and addition of things like GitHub template files.

This release merely changes the version of httpx required by `requirements.txt`. No other changes.

This version adds a missing internal function definition in `download(...)`.

This version changes `pluralized` so that it outputs `0 items` instead of `0 item` if the number of its argument has length 0.

This version adds more test cases and splits out the requirements for testing/development into a separate requirements file, [`requirements-dev.txt`](requirements-dev.txt).