Revert "switch to Qt5"

This reverts commit fbcfa54.

Author: skvark

setup.py

@@ -123,12 +123,9 @@ def main():
     ] + (["-DOPENCV_EXTRA_MODULES_PATH=" + os.path.abspath("opencv_contrib/modules")] if build_contrib else [])
 
     # OS-specific components
-    if sys.platform.startswith('linux') and not build_headless:
+    if (sys.platform == 'darwin' or sys.platform.startswith('linux')) and not build_headless:
         cmake_args.append("-DWITH_QT=4")
 
-    if sys.platform == 'darwin' and not build_headless:
-        cmake_args.append("-DWITH_QT=5")
-
     if build_headless:
         # it seems that cocoa cannot be disabled so on macOS the package is not truly headless
         cmake_args.append("-DWITH_WIN32UI=OFF")

travis_config.sh

@@ -96,11 +96,13 @@ function pre_build {
         brew_add_local_bottles
     fi
 
-    echo 'Installing qt5'
+    echo 'Installing QT4'
+    brew tap | grep -qxF cartr/qt4 || brew tap cartr/qt4
     if [ -n "$CACHE_STAGE" ]; then
-        brew_install_and_cache_within_time_limit qt5 || { [ $? -gt 1 ] && return 2 || return 0; }
+        brew_install_and_cache_within_time_limit cartr/qt4/qt@4 || { [ $? -gt 1 ] && return 2 || return 0; }
     else
-        brew install qt5
+        brew tap --repair
+        brew install cartr/qt4/qt@4
     fi
 
     echo 'Installing FFmpeg'