Use a temporary file for testing defaults.ini content loading in test_pypi_sourcecode_analyzer.py

Description

In this test module - https://github.com/oracle/macaron/blob/612e27ec347e7e073311b65a32b9eec8c6ba7d5c/tests/malware_analyzer/pypi/test_pypi_sourcecode_analyzer.py, we are mocking the defaults object to test some behaviors relating to some source code analysis configuration in defaults.ini.

Expectation

In this module https://github.com/oracle/macaron/blob/44dbf0acbd3dcb9f577db97b5c6876cfb8c87957/tests/config/test_defaults.py we put the defaults.ini content into a temporary file and load from it.
This is an example https://github.com/oracle/macaron/blob/44dbf0acbd3dcb9f577db97b5c6876cfb8c87957/tests/config/test_defaults.py#L103-L109

which can remove the need for mocking and keep the defaults.ini in the test definition itself. Perhaps we can rewrite the tests in test_pypi_sourcecode_analyzer.py to use this approach instead.