just use the raw url directly

Author: skvark

travis_config.sh

@@ -105,8 +105,7 @@ function pre_build {
     if [ -n "$CACHE_STAGE" ]; then
         echo "Qt5 has bottle, no caching needed"
     else
-        brew extract qt --version=5.13.2
-        brew install [email protected]
+        brew install https://raw.githubusercontent.com/Homebrew/homebrew-core/079ce55db79acc87b91bec950249595b1584e119/Formula/qt.rb
         export PATH="/usr/local/opt/qt/bin:$PATH"
     fi