Comment 13 for bug 1651812

For people with this issue:
"file:///build/webbrowser-app-4Hx99o/webbrowser-app-0.23+16.04.20160413/src/app/webcontainer/webapp-container.qml:-1 File not found\n"

it's likely because you're building the snap against an older Ubuntu like 16.04; in this case, you need to add a PPA first:
sudo add-apt-repository ppa:ci-train-ppa-service/stable-phone-overlay && sudo apt update