Yarn failed on Windows os environment

Hey!

Recently, I tried to build a electron app (https://github.com/liudonghua123/system-network-info) on travis-ci, here is the .travis.yml.

And in build log console, it always gave me following error.

$ yarn
yarn install v1.12.1
[1/4] Resolving packages...
[2/4] Fetching packages...
info There appears to be trouble with your network connection. Retrying...
info There appears to be trouble with your network connection. Retrying...
info There appears to be trouble with your network connection. Retrying...
info There appears to be trouble with your network connection. Retrying...
info There appears to be trouble with your network connection. Retrying...
info There appears to be trouble with your network connection. Retrying...
info There appears to be trouble with your network connection. Retrying...
info There appears to be trouble with your network connection. Retrying...
info There appears to be trouble with your network connection. Retrying...
info There appears to be trouble with your network connection. Retrying...

I have tried yarn config list, yarn config delete proxy, yarn install --network-timeout 1000000, but none of them helps.

so, removing yarn.lock and then

before_install:
  - yarn config delete proxy
  - npm config rm proxy
  - npm config rm https-proxy

got this working for us! I’m not sure if yarn.lock removal is necessary. I’m testing that out now.