test: comment description about test environment variable

Signed-off-by: Carl Flottmann <carl.flottmann@oracle.com>

Author: art1f1c3R

tests/malware_analyzer/pypi/test_fake_email.py

@@ -12,6 +12,11 @@
 from macaron.malware_analyzer.pypi_heuristics.heuristics import HeuristicResult
 from macaron.malware_analyzer.pypi_heuristics.metadata.fake_email import FakeEmailAnalyzer
 
+# Note: throughout these unit tests we set email_validator.TEST_ENVIRONMENT to True. This sets a global
+# environment variable in email_validator that ensures that all calls to validate_email have
+# test_environment=True set. This allows test and **.test domains and disables DNS deliverability checks
+# (so disables check_deliverability=true). See https://github.com/JoshData/python-email-validator for more.
+
 
 @pytest.fixture(name="analyzer")
 def analyzer_() -> FakeEmailAnalyzer: