This fixes up the following problems:
1. Using string concatenation instead of the formatting variant methods.
2. Logging or swallowing exception messages without logging the exception
itself (this swallows the stack trace).
3. Unnecessary logging on re-thrown exceptions.
4. Unnecessary use of formatting variant methods when not necessary.
5. Complicated logging statements involving significant processing not being
wrapped inside of a logging level check.
6. Redundant logging both of an exception itself and its message (this is
unnecessary duplication).
7. Use of the base Logger class instead of our FormattingLogger class.
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=182419837
Refactor the auth code into its own dagger module, add tests and use the new interfaces to implement the login and logout commands.
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=149108266
