Although the GSON version in repositories.bzl was 2.8.5, the same name
(com_google_code_gson) was apparently used internally for version 2.7 for some
dependency of com.google.closure (soy?)
Changed the name, and it solved the problem. The new name is also "more
correct" as the package is com.google.gson, not com.google.code.gson.
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=250313017
44ccd45439