Added file based check for sourcing venv activate script in bashrc

[kumaramit-msft]

• [ ] The purpose of this PR is explained in this message or in an issue. If an issue please include a reference as #<issue_number>.
• [ ] Tests are included and/or updated for code changes.
• [ ] Proper license headers are included in each file.

[kumaramit-msft]

This fixes error for python apps if virtual env is not present