Node v6.0.0 ships with npm 3.8.3.
Node v6.9.1 (currently in Jenkins; T155443) ships with npm 3.10.8.
However, our Nodepool images have npm 2.15.2 pre-installed. This is a rather odd combination.
npm 3 no more installs peer dependencies, they thus have to be explicitly defined in `package.json`. From Jenkins build log as of July 31th:
```
grep -Z -l peerDependencies /srv/jenkins/builds/*npm*/*/log|xargs -0 -n1 grep 'Cloning repository'|cut -d\/ -f4-|sort|uniq -c
2 labs/tools/heritage
26 mediawiki/extensions/3D
32 mediawiki/extensions/AbuseFilter
27 mediawiki/extensions/AdvancedSearch
4 mediawiki/extensions/ApiFeatureUsage
12 mediawiki/extensions/ArticlePlaceholder
8 mediawiki/extensions/Babel
4 mediawiki/extensions/BetaFeatures
2 mediawiki/extensions/BoilerPlate
2 mediawiki/extensions/Calendar
4 mediawiki/extensions/Capiunto
6 mediawiki/extensions/CategoryTree
28 mediawiki/extensions/CentralAuth
30 mediawiki/extensions/CentralNotice
4 mediawiki/extensions/CharInsert
118 mediawiki/extensions/CirrusSearch
6 mediawiki/extensions/Cite
2 mediawiki/extensions/CiteThisPage
6 mediawiki/extensions/Citoid
4 mediawiki/extensions/CleanChanges
2 mediawiki/extensions/CodeEditor
57 mediawiki/extensions/CodeMirror
4 mediawiki/extensions/CodeReview
11 mediawiki/extensions/CollaborationKit
14 mediawiki/extensions/Collection
4 mediawiki/extensions/ConfirmEdit
4 mediawiki/extensions/ContributionTracking
3 mediawiki/extensions/DismissableSiteNotice
135 mediawiki/extensions/DonationInterface
125 mediawiki/extensions/Echo
13 mediawiki/extensions/EducationProgram
4 mediawiki/extensions/ElectronPdfService
11 mediawiki/extensions/EventLogging
9 mediawiki/extensions/ExtensionDistributor
19 mediawiki/extensions/FileImporter
15 mediawiki/extensions/FlaggedRevs
37 mediawiki/extensions/Flow
3 mediawiki/extensions/GettingStarted
6 mediawiki/extensions/GlobalPreferences
3 mediawiki/extensions/GlobalUserPage
7 mediawiki/extensions/Graph
3 mediawiki/extensions/GuidedTour
46 mediawiki/extensions/GWToolset
7 mediawiki/extensions/InputBox
4 mediawiki/extensions/Interwiki
4 mediawiki/extensions/JsonConfig
4 mediawiki/extensions/MassMessage
29 mediawiki/extensions/Math
25 mediawiki/extensions/MobileApp
104 mediawiki/extensions/MobileFrontend
19 mediawiki/extensions/MultimediaViewer
22 mediawiki/extensions/Newsletter
8 mediawiki/extensions/OATHAuth
6 mediawiki/extensions/OAuth
11 mediawiki/extensions/OpenStackManager
24 mediawiki/extensions/ORES
9 mediawiki/extensions/PageTriage
12 mediawiki/extensions/ParserMigration
4 mediawiki/extensions/PerformanceInspector
4 mediawiki/extensions/Petition
71 mediawiki/extensions/Popups
16 mediawiki/extensions/ProofreadPage
5 mediawiki/extensions/QuickSurveys
29 mediawiki/extensions/Quiz
26 mediawiki/extensions/ReadingLists
71 mediawiki/extensions/RevisionSlider
7 mediawiki/extensions/Score
9 mediawiki/extensions/Scribunto
11 mediawiki/extensions/SecurePoll
13 mediawiki/extensions/ShortUrl
18 mediawiki/extensions/SyntaxHighlight_GeSHi
6 mediawiki/extensions/TemplateData
7 mediawiki/extensions/TemplateSandbox
8 mediawiki/extensions/TimedMediaHandler
5 mediawiki/extensions/timeline
6 mediawiki/extensions/TocTree
10 mediawiki/extensions/Translate
22 mediawiki/extensions/TwoColConflict
19 mediawiki/extensions/UniversalLanguageSelector
18 mediawiki/extensions/UploadWizard
4 mediawiki/extensions/UrlShortener
4 mediawiki/extensions/VipsScaler
56 mediawiki/extensions/VisualEditor
499 mediawiki/extensions/Wikibase
18 mediawiki/extensions/WikibaseMediaInfo
231 mediawiki/extensions/WikibaseQualityConstraints
2 mediawiki/extensions/Wikidata.org
4 mediawiki/extensions/WikidataPageBanner
8 mediawiki/extensions/WikiEditor
4 mediawiki/extensions/wikihiero
4 mediawiki/extensions/WikiLove
4 mediawiki/extensions/WikimediaBadges
1 mediawiki/extensions/WikimediaEvents
6 mediawiki/extensions/WikimediaIncubator
18 mediawiki/extensions/WikimediaMessages
20 mediawiki/extensions/Wikispeech
5 mediawiki/extensions/ZeroBanner
4 mediawiki/extensions/ZeroPortal
15 mediawiki/services/mobileapps/deploy
146 mediawiki/services/parsoid
2 mediawiki/services/trending-edits
4 mediawiki/services/trending-edits/deploy
4 mediawiki/skins/apex
4 mediawiki/skins/CologneBlue
145 mediawiki/skins/MinervaNeue
4 mediawiki/skins/Modern
11 mediawiki/skins/MonoBook
4 mediawiki/skins/Nostalgia
6 mediawiki/skins/Timeless
90 mediawiki/skins/Vector
26 VisualEditor/VisualEditor
153 wikidata/query/gui
6 wikimedia/portals
```