Proposal: Make robotframework-stacktrace an optional dependency

[xtergo]

Hi,

I'd like to propose making robotframework-stacktrace an optional dependency rather than a hard requirement.

Background: The robotframework-stacktrace package (MarketSquare/robotframework-stacktrace) appears to have limited maintenance activity - the last release (0.4.1) was in June 2021, and there's minimal recent development. For organizations with strict dependency policies around unmaintained packages, this creates a blocker for adopting pabot.

Current behavior: Pabot automatically adds RobotStackTracer as a default listener when no other listener is specified. While this is a nice debugging enhancement, it's not essential for core functionality.

Proposed solution:

Move robotframework-stacktrace from install_requires to extras_require
Add a graceful fallback when the package isn't installed
Users who want the feature can install with pip install robotframework-pabot[stacktrace]
This approach:

Maintains backward compatibility for existing users
Removes the hard dependency for users who don't need it
Keeps the feature available for those who want it

[joonaskuisma]

Good idea! I will create a separate issue for this.
Additionally, we could remove the natsort dependency at the same time, since it is only used in one place and can be replaced with a pure Python implementation.

[joonaskuisma]

#699 Created