ng update return error for private package

[tiaguinho]

Version

Angular CLI: 6.0.0
Node: 8.9.4
OS: darwin x64 (Sierra)

Repro steps

ng update @angular/cli

I have an Angular CLI project with a few private packages using YARN workpaces.
I'm receiving the error Not found: PACKAGE_NAME when I try to use ng update.

[clydin]

Duplicate of #10614

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