Errors I get today when running the tool:

% tools/licenses.py --target-os android --depfile out/Debug/gen/components/resources/about_credits.d credits licenses.html
third_party/spirv-headers errors:
 License file not found. Either add a file named LICENSE, import upstream's COPYING if available, or add a 'License File:' line to README.chromium with the appropriate path.
third_party/glslang-angle errors:
 License file not found. Either add a file named LICENSE, import upstream's COPYING if available, or add a 'License File:' line to README.chromium with the appropriate path.
missing README.chromium or licenses.py SPECIAL_CASES entry in tools/binary_size/libsupersize/testdata/mock_output_directory/obj/third_party/icu
third_party/android_ndk errors:
 License file not found. Either add a file named LICENSE, import upstream's COPYING if available, or add a 'License File:' line to README.chromium with the appropriate path.
missing README.chromium or licenses.py SPECIAL_CASES entry in third_party/ink
missing README.chromium or licenses.py SPECIAL_CASES entry in chrome/common/extensions/docs/server2/third_party/json_schema_compiler
third_party/metrics_proto errors:
 couldn't find 'URL' line in README.chromium or licences.py SPECIAL_CASES
missing README.chromium or licenses.py SPECIAL_CASES entry in third_party/blink
missing README.chromium or licenses.py SPECIAL_CASES entry in third_party/libexif
third_party/win_build_output errors:
 couldn't find 'URL' line in README.chromium or licences.py SPECIAL_CASES
third_party/vulkan-validation-layers errors:
 License file not found. Either add a file named LICENSE, import upstream's COPYING if available, or add a 'License File:' line to README.chromium with the appropriate path.
missing README.chromium or licenses.py SPECIAL_CASES entry in third_party/depot_tools
third_party/android_system_sdk errors:
 couldn't find 'URL' line in README.chromium or licences.py SPECIAL_CASES
missing README.chromium or licenses.py SPECIAL_CASES entry in third_party/scan-build
missing README.chromium or licenses.py SPECIAL_CASES entry in third_party/cardboard-java
missing README.chromium or licenses.py SPECIAL_CASES entry in third_party/libjingle
third_party/spirv-tools-angle errors:
 License file not found. Either add a file named LICENSE, import upstream's COPYING if available, or add a 'License File:' line to README.chromium with the appropriate path.
missing README.chromium or licenses.py SPECIAL_CASES entry in chrome/common/extensions/docs/server2/third_party/cloudstorage

These errors seem to get swallowed in normal builds, but they seem avoidable easily by adding or updating README files. http://crrev.com/c/822612 is starting to print them in regular builds, so we should fix them to clean up logs.