Improve jinja template error handling in metadata.py

[milahu]

Enhance error reporting for jinja template rendering failures by including the line number and context of the error.

example

before

Error: Failed to render jinja template in /home/user/src/milahu/conda-recipes/recipes/miniupnpc/meta.yaml:
unexpected '}'

after

Error: Failed to render jinja template in /home/user/src/milahu/conda-recipes/recipes/miniupnpc/meta.yaml:
TemplateSyntaxError: unexpected '}' in line 44
41:     mv -v $PREFIX/bin/upnpc-shared $PREFIX/bin/upnpc
42:     mv -v $PREFIX/bin/upnp-listdevices-shared $PREFIX/bin/upnp-listdevices
43:     rm -v $PREFIX/bin/external-ip.sh
44:     {% endif }
45: 
46: requirements:
47:   build:

Description

Checklist - did you ...

• Add a file to the news directory (using the template) for the next release's release notes?
• Add / update necessary tests?
• Add / update outdated documentation?

[conda-bot]

We require contributors to sign our Contributor License Agreement and we don't have one on file for @milahu.

In order for us to review and merge your code, please e-sign the Contributor License Agreement PDF. We then need to manually verify your signature, merge the PR (conda/infrastructure#1340), and ping the bot to refresh the PR.

[travishathaway]

@conda-bot check

[travishathaway]

Hi @milahu,

We appreciate you taking the effort to submit a pull request, but I just want to let you know that this is unlikely to be merged in its current shape. If you'd like to find another issue to work on, I'd recommend joining our chat over at Zulip and maybe swinging by the #build-tools channel to see what folks are working on and need help with.

[milahu]

this is unlikely to be merged in its current shape

what is wrong with the current shape?