Running ./mwaa-local-env package-requirements will always result in an exit code of 0, even on failure.

Steps to Reproduce:
Note: All steps were performed using v2.8.1, but the behavior should be the same for all versions that include this function (v2.2.2+).

1. Modify requirements.txt to force a failure. E.g. add apache-airflow-providers-datadog==3.5.0 to the requirements.txt included in the repo.

2. Run ./mwaa-local-env package-requirements and check exit code.

   Click here for shell output

    ➜  aws-mwaa-local-runner git:(v2.8.1) ✗ ./mwaa-local-env package-requirements 
   Container amazon/mwaa-local:2_8 exists. Skipping build
   Packaging requirements.txt into plugins
   Collecting apache-airflow-providers-snowflake==5.2.1
     Downloading apache_airflow_providers_snowflake-5.2.1-py3-none-any.whl (37 kB)
   Collecting apache-airflow-providers-mysql==5.5.1
     Downloading apache_airflow_providers_mysql-5.5.1-py3-none-any.whl (25 kB)
   ERROR: Cannot install apache-airflow-providers-datadog==3.5.0 because these package versions have conflicting dependencies.
   
   The conflict is caused by:
       The user requested apache-airflow-providers-datadog==3.5.0
       The user requested (constraint) apache-airflow-providers-datadog==3.5.1
   
   To fix this you could try to:
   1. loosen the range of package versions you've specified
   4. remove package versions to allow pip attempt to solve the dependency conflict
   
   ERROR: ResolutionImpossible: for help visit https://pip.pypa.io/en/latest/topics/dependency-resolution/#dealing-with-dependency-conflicts
   
   [notice] A new release of pip available: 22.3.1 -> 24.2
   [notice] To update, run: pip install --upgrade pip
   updating: README.md (deflated 37%)
   
    ➜  aws-mwaa-local-runner git:(v2.8.1) ✗ echo $?
   0

Note that ./mwaa-local-env test-requirements does have a proper non-zero exit code on failure. However both commands should have a non-zero exit code on failure.

 ➜  aws-mwaa-local-runner git:(v2.8.1) ✗ ./mwaa-local-env test-requirements    
Container amazon/mwaa-local:2_8 exists. Skipping build
--constraint "https://raw.githubusercontent.com/apache/airflow/constraints-2.8.1/constraints-3.11.txt"
Installing requirements.txt
Collecting apache-airflow-providers-snowflake==5.2.1
  Downloading apache_airflow_providers_snowflake-5.2.1-py3-none-any.whl (37 kB)
Collecting apache-airflow-providers-mysql==5.5.1
  Downloading apache_airflow_providers_mysql-5.5.1-py3-none-any.whl (25 kB)
ERROR: Cannot install apache-airflow-providers-datadog==3.5.0 because these package versions have conflicting dependencies.

The conflict is caused by:
    The user requested apache-airflow-providers-datadog==3.5.0
    The user requested (constraint) apache-airflow-providers-datadog==3.5.1

To fix this you could try to:
1. loosen the range of package versions you've specified
2. remove package versions to allow pip attempt to solve the dependency conflict

ERROR: ResolutionImpossible: for help visit https://pip.pypa.io/en/latest/topics/dependency-resolution/#dealing-with-dependency-conflicts

[notice] A new release of pip available: 22.3.1 -> 24.2
[notice] To update, run: pip install --upgrade pip

 ➜  aws-mwaa-local-runner git:(v2.8.1) ✗ echo $?                            
1

Cause:
The issue stems from the package_requirements() function in entrypoint.sh. Specifically, there is no check that pip3 download -r ... completed successfully. The script will just attempt to zip whatever was downloaded and continue on it's way.

Fix:
I'm working on a fix for this and will open a PR to v2.9.2 when it is ready. I kindly request the fix be merged to lower branches (either all v2.2.2+ or at least to the branches for versions that are still supported).

Thank you!