[DRE-maint] Bug#894072: gitlab: postinst fails with "/var/lib/gitlab/yarn/node_modules/.bin/yarn: not found"

[Dmitry Smirnov]

Package: gitlab
Version: 10.5.5+dfsg-3
Severity: serious

Installation of GitLab failed in postinst as follows:

~~~~
Installing node modules...
npm WARN package.json compression-webpack-plugin at 0.3.2 No license field.
npm WARN package.json dropzone at 4.3.0 No license field.
npm WARN package.json jszip-utils at 0.0.2 license should be a valid SPDX
license expression
npm WARN package.json select2 at 3.5.2-browserify No license field.
yarn at 1.5.1 ../node_modules/yarn
sh: 1: /var/lib/gitlab/yarn/node_modules/.bin/yarn: not found
dpkg: error processing package gitlab (--configure):
 subprocess installed post-installation script returned error exit
status 127
~~~~