test: fix test failures caused by HTTP status codes differences

[shuuji3]

fixes #14

The tests were failing due to the differences in HTTP response codes. Now, the API server returns 401 Unauthorized when the API token is incorrect.

Test results in local

[theguardian-api-python]  test/replace-403-with-401 (9eb136d) via  v3.11.5
|> python test.py -v
test_content_get_result_with_exception (test_content.TestContent.test_content_get_result_with_exception) ... ok
test_content_response_failure_incorrect_api_key (test_content.TestContent.test_content_response_failure_incorrect_api_key) ... ok
test_content_response_header (test_content.TestContent.test_content_response_header) ... ok
test_content_response_success_correct_details (test_content.TestContent.test_content_response_success_correct_details) ... ok
test_content_results (test_content.TestContent.test_content_results) ... ok
test_content_with_headers (test_content.TestContent.test_content_with_headers) ... ok
test_contents_find_by_id_correct_url (test_content.TestContent.test_contents_find_by_id_correct_url) ... ok
test_contents_find_by_id_incorrect_url (test_content.TestContent.test_contents_find_by_id_incorrect_url) ... ok
test_section_get_references_correct_pages (test_content.TestContent.test_section_get_references_correct_pages) ... ok
test_section_get_references_incorrect_pages (test_content.TestContent.test_section_get_references_incorrect_pages) ... ok
test_edition_get_direct_content (test_edition.TestEdition.test_edition_get_direct_content) ... ok
test_edition_get_indirect_content (test_edition.TestEdition.test_edition_get_indirect_content) ... ok
test_edition_get_indirect_content_invalid_credentials (test_edition.TestEdition.test_edition_get_indirect_content_invalid_credentials) ... ok
test_edition_get_response_section_count (test_edition.TestEdition.test_edition_get_response_section_count) ... ok
test_edition_get_result_with_exception (test_edition.TestEdition.test_edition_get_result_with_exception) ... ok
test_edition_get_result_without_exception (test_edition.TestEdition.test_edition_get_result_without_exception) ... ok
test_edition_response_failure_incorrect_api_key (test_edition.TestEdition.test_edition_response_failure_incorrect_api_key) ... ok
test_edition_response_success_correct_details (test_edition.TestEdition.test_edition_response_success_correct_details) ... ok
test_edition_url (test_edition.TestEdition.test_edition_url) ... ok
test_section_get_direct_content (test_section.TestSection.test_section_get_direct_content) ... ok
test_section_get_indirect_content (test_section.TestSection.test_section_get_indirect_content) ... ok
test_section_get_indirect_content_invalid_credentials (test_section.TestSection.test_section_get_indirect_content_invalid_credentials) ... ok
test_section_get_result_with_exception (test_section.TestSection.test_section_get_result_with_exception) ... ok
test_section_get_result_without_exception (test_section.TestSection.test_section_get_result_without_exception) ... ok
test_section_response_failure_incorrect_api_key (test_section.TestSection.test_section_response_failure_incorrect_api_key) ... ok
test_section_response_success_correct_details (test_section.TestSection.test_section_response_success_correct_details) ... ok
test_section_get_references_correct_pages (test_tag.TestTag.test_section_get_references_correct_pages) ... ok
test_section_get_references_incorrect_pages (test_tag.TestTag.test_section_get_references_incorrect_pages) ... ok
test_tag_get_direct_content (test_tag.TestTag.test_tag_get_direct_content) ... ok
test_tag_get_indirect_content (test_tag.TestTag.test_tag_get_indirect_content) ... ok
test_tag_get_indirect_content_invalid_credentials (test_tag.TestTag.test_tag_get_indirect_content_invalid_credentials) ... ok
test_tag_get_result_with_exception (test_tag.TestTag.test_tag_get_result_with_exception) ... ok
test_tag_get_result_without_exception (test_tag.TestTag.test_tag_get_result_without_exception) ... ok
test_tag_response_failure_incorrect_api_key (test_tag.TestTag.test_tag_response_failure_incorrect_api_key) ... ok
test_tag_response_success_correct_details (test_tag.TestTag.test_tag_response_success_correct_details) ... ok
test_tag_url (test_tag.TestTag.test_tag_url) ... ok

----------------------------------------------------------------------
Ran 36 tests in 37.939s

OK