--errorLevel 2 option with -du doesn't work as expected

[jschirrmacher]

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Steps to Reproduce

.ncurc: empty

Steps:

Current Behavior

When running ncu --errorLevel 2 -du on a clean repository, ncu installs dependencies and runs tests (successfully), then tries to update the dependencies and re-run tests. It prints out

Upgrading all dependencies and re-running tests
ncu --errorLevel 2 -du
Error: 
Dependencies not up-to-date
    at _e (/Users/joschi/.npm/_npx/0a80f0fb114540fe/node_modules/npm-check-updates/build/index.js:450:1731)
    at fle (/Users/joschi/.npm/_npx/0a80f0fb114540fe/node_modules/npm-check-updates/build/index.js:541:831)
    at async Gre (/Users/joschi/.npm/_npx/0a80f0fb114540fe/node_modules/npm-check-updates/build/index.js:450:4938)

It all works well when called without --errorLevel 2 or with any other error level value.