Suppress color output when writing to something other than a terminal. #51
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It’s awkward to parse migration-verifier logs in editors and pagers that don’t handle ANSI escape sequences. This changeset alters migration-verifier’s logging so that it only colorizes when outputting to a terminal.
For now this causes
go test’s output to be uncolorized. If it seems gainful we could put in some special escape mechanism to preserve color undergo test.