fix(NewRelicContextFormatter): add cause and context to stack traces

[sweco]

Overview

NewRelicContextFormatter logs stack traces without causes which makes many errors hard to debug.

Let's take a look at the following code:

try:
    try:
        raise ValueError("First exception")
    except:
        raise ValueError("Second exception")
except Exception as e:
    logging.error("Encountered error", exc_info=e)

Before the PR, the exception message looked as follows:

  File ".../newrelic_exception_cause.py", line 60, in <module>
    raise ValueError("Second exception")

After the PR, it shows more details on the first cause:

Traceback (most recent call last):
  File ".../newrelic_exception_cause.py", line 58, in <module>
    raise ValueError("First exception")
ValueError: First exception
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
  File ".../newrelic_exception_cause.py", line 60, in <module>
    raise ValueError("Second exception")
ValueError: Second exception

Related Github Issue

No Github issue created.

Testing

Tests were updated to test a particular case where exception has a cause.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
2 out of 3 committers have signed the CLA.

✅ sweco
✅ TimPansino
❌ mergify[bot]
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[TimPansino]

We'll give this a review after the US holiday season is over, we're going to avoid the risk of changing anyone's logs during this time period.