Build fails if mupignore excludes package.json

[steph643]

If the .mupignore file excludes package.json, you get the following error:

Started TaskList: Pushing App
[vpsXXXXXX.ovh.net] - Pushing App bundle to the Server
[vpsXXXXXX.ovh.net] - Pushing App bundle to the Server: SUCCESS
[vpsXXXXXX.ovh.net] - Build Image
[vpsXXXXXX.ovh.net] x Build Image: FAILED
------------------------------------STDERR------------------------------------
COPY failed: stat /var/lib/docker/tmp/docker-builder099874800/package.json: no such file or directory
------------------------------------STDOUT------------------------------------
10.11.0: Pulling from library/node
Digest: sha256:32d5d5435e5038028bd0c0871d256d5887b06c4315cb1a135bcf81e0735627c9
Status: Image is up to date for node:10.11.0
docker.io/library/node:10.11.0
Building image
Sending build context to Docker daemon  110.6kB
Step 1/9 : FROM node:10.11.0
---> 8672b25e842c
Step 2/9 : RUN mkdir -p /home/node/app || true
---> Using cache
---> feae69ebe526
Step 3/9 : WORKDIR /home/node/app
---> Using cache
---> 2546de041258
Step 4/9 : ENV    PORT=80    VIRTUAL_HOST=*.docuss.org    HTTPS_METHOD=n
oredirect    HTTP_FORWARDED_COUNT=1    NODE_ENV=production
---> Using cache
---> ab768c7aaa40
Step 5/9 : COPY ./package.json ./package.json
------------------------------------------------------------------------------

Solution: don't exclude package.json.

Tested under Windows 7.