lint: avoid false positives with custom errors-package

[leonelquinteros]

When using errors.New(fmt.Sprintf(...)),
lint will alert that you should use fmt.Errorf(...).

Before this patch, this alert was also displayed
when using a custom errors-package.
There are valid use cases to use errors.New(fmt.Sprintf(...))
in a custom errors-package context.

This patch avoids the "false positive" alert
when a custom errors-package is imported in the current file.

Fixes #350

[andybons]

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Message from Andrew Bonventre:

Patch Set 1:

(3 comments)

This should have an associated test

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Message from Leonel Quinteros:

Patch Set 2:

(3 comments)

Patch Set 1:

(3 comments)

This should have an associated test

Added a test case to cover the allowed cases when importing a custom errors package. The other cases are already covered in the test suite.

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Message from Andrew Bonventre:

Patch Set 3:

(1 comment)

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Message from Leonel Quinteros:

Patch Set 3:

Patch Set 3:

(1 comment)

Sorry, somehow the git commit --amend I did, created a new commit instead of updating the original message: cac6d06

Let me try to fix that.

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Uploaded patch set 4: Commit message was updated.

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Uploaded patch set 5: Commit message was updated.

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Message from Andrew Bonventre:

Patch Set 5:

The commit message for a PR is determined from the title and first comment of the PR, not the commit message itself: https://github.com/golang/go/wiki/GerritBot#how-does-gerritbot-determine-the-final-commit-message

This is because there could be multiple commit messages in a PR, so it’s hard to determine which one should be used.

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Message from Leonel Quinteros:

Patch Set 5:

Patch Set 3:

(1 comment)

OK, now i've rebased the branch, edited the commit messages and force-pushed the changes so it looks better to me.

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Message from Leonel Quinteros:

Patch Set 5:

Patch Set 5:

The commit message for a PR is determined from the title and first comment of the PR, not the commit message itself: https://github.com/golang/go/wiki/GerritBot#how-does-gerritbot-determine-the-final-commit-message

This is because there could be multiple commit messages in a PR, so it’s hard to determine which one should be used.

Oh! Totally missed that. Thanks for the clarification. Quickly-editing right now.

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Message from Gerrit Bot:

Uploaded patch set 6: Commit message was updated.

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Message from Andrew Bonventre:

Patch Set 6:

(1 comment)

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Message from Gerrit Bot:

Uploaded patch set 7: Commit message was updated.

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Message from Andrew Bonventre:

Patch Set 7: Code-Review+1

(1 comment)

Ready for you, Alan.

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Message from Andrew Bonventre:

Patch Set 8:

(2 comments)

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Uploaded patch set 9: Commit message was updated.

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Message from Andrew Bonventre:

Patch Set 9: Code-Review+2

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This PR is being closed because golang.org/cl/96091 has been merged.