added insert tag for handle-errors tutorial

[evank28]

Very simple addition of a highlight in the tutorial, to communicate addition of this additional variable assignment.

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[evank28]

@googlebot I signed it!

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Message from Dmitri Shuralyov:

Patch Set 2: Run-TryBot+1

(4 comments)

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TryBots beginning. Status page: https://farmer.golang.org/try?commit=ddf07a5a

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Patch Set 2:

Build is still in progress...
This change failed on linux-amd64 (Go 1.15.x):
See https://storage.googleapis.com/go-build-log/9b955d2d/linux-amd64_f3a0faf3.log

Other builds still in progress; subsequent failure notices suppressed until final report. Consult https://build.golang.org/ to see whether they are new failures. Keep in mind that TryBots currently test exactly your git commit, without rebasing. If your commit's git parent is old, the failure might've already been fixed.

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Message from Go Bot:

Patch Set 2: TryBot-Result-1

9 of 9 TryBots failed:
Failed on linux-amd64 (Go 1.15.x): https://storage.googleapis.com/go-build-log/9b955d2d/linux-amd64_f3a0faf3.log
Failed on linux-amd64 (Go 1.14.x): https://storage.googleapis.com/go-build-log/6eed7d36/linux-amd64_b923928b.log
Failed on freebsd-amd64-12_0: https://storage.googleapis.com/go-build-log/41d8e61a/freebsd-amd64-12_0_98823619.log
Failed on linux-amd64: https://storage.googleapis.com/go-build-log/41d8e61a/linux-amd64_ade6871b.log
Failed on linux-386: https://storage.googleapis.com/go-build-log/41d8e61a/linux-386_062ae6ed.log
Failed on openbsd-amd64-64: https://storage.googleapis.com/go-build-log/41d8e61a/openbsd-amd64-64_3b8c0427.log
Failed on linux-amd64-race: https://storage.googleapis.com/go-build-log/41d8e61a/linux-amd64-race_e5f8c056.log
Failed on windows-amd64-2016: https://storage.googleapis.com/go-build-log/41d8e61a/windows-amd64-2016_8fea0d31.log
Failed on windows-386-2008: https://storage.googleapis.com/go-build-log/41d8e61a/windows-386-2008_12c1d543.log

Consult https://build.golang.org/ to see whether they are new failures. Keep in mind that TryBots currently test exactly your git commit, without rebasing. If your commit's git parent is old, the failure might've already been fixed.

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Message from Dmitri Shuralyov:

Patch Set 2: Run-TryBot+1

(4 comments)

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Patch Set 2:

TryBots beginning. Status page: https://farmer.golang.org/try?commit=ddf07a5a

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Message from Go Bot:

Patch Set 2:

Build is still in progress...
This change failed on linux-amd64 (Go 1.15.x):
See https://storage.googleapis.com/go-build-log/9b955d2d/linux-amd64_f3a0faf3.log

Other builds still in progress; subsequent failure notices suppressed until final report. Consult https://build.golang.org/ to see whether they are new failures. Keep in mind that TryBots currently test exactly your git commit, without rebasing. If your commit's git parent is old, the failure might've already been fixed.

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[gopherbot]

Message from Go Bot:

Patch Set 2: TryBot-Result-1

9 of 9 TryBots failed:
Failed on linux-amd64 (Go 1.15.x): https://storage.googleapis.com/go-build-log/9b955d2d/linux-amd64_f3a0faf3.log
Failed on linux-amd64 (Go 1.14.x): https://storage.googleapis.com/go-build-log/6eed7d36/linux-amd64_b923928b.log
Failed on freebsd-amd64-12_0: https://storage.googleapis.com/go-build-log/41d8e61a/freebsd-amd64-12_0_98823619.log
Failed on linux-amd64: https://storage.googleapis.com/go-build-log/41d8e61a/linux-amd64_ade6871b.log
Failed on linux-386: https://storage.googleapis.com/go-build-log/41d8e61a/linux-386_062ae6ed.log
Failed on openbsd-amd64-64: https://storage.googleapis.com/go-build-log/41d8e61a/openbsd-amd64-64_3b8c0427.log
Failed on linux-amd64-race: https://storage.googleapis.com/go-build-log/41d8e61a/linux-amd64-race_e5f8c056.log
Failed on windows-amd64-2016: https://storage.googleapis.com/go-build-log/41d8e61a/windows-amd64-2016_8fea0d31.log
Failed on windows-386-2008: https://storage.googleapis.com/go-build-log/41d8e61a/windows-386-2008_12c1d543.log

Consult https://build.golang.org/ to see whether they are new failures. Keep in mind that TryBots currently test exactly your git commit, without rebasing. If your commit's git parent is old, the failure might've already been fixed.

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Please don’t reply on this GitHub thread. Visit golang.org/cl/277454.
After addressing review feedback, remember to publish your drafts!