package/ci: make code coverage actually work on macOS.

This went undiscovered for quite a long time.

package/ci/travis.yml

@@ -109,9 +109,6 @@ install:
 - if [ "$TRAVIS_OS_NAME" == "linux" ]; then export PATH=$HOME/cmake/bin:$PATH && cmake --version; fi
 - if [ "$TRAVIS_OS_NAME" == "osx" ]; then HOMEBREW_NO_AUTO_UPDATE=1 brew install ninja; fi
 
-# Code coverage of python bindings
-- if [ "$TRAVIS_OS_NAME" == "linux" ] || [ "$TRAVIS_OS_NAME" == "osx" ]; then pip3 install coverage codecov; fi
-
 # pybind11 (cached). On macOS the version 2.3.0 needs a brew update, the stale
 # Travis image has just 2.2.4.
 - if [ "$TRAVIS_OS_NAME" == "linux" ] && [ ! -e "$HOME/pybind11/bin" ]; then $TRAVIS_BUILD_DIR/package/ci/setup-pybind11.sh; fi
@@ -125,6 +122,11 @@ install:
 # visible.
 - if [ "$TRAVIS_OS_NAME" == "osx" ]; then brew upgrade numpy; fi
 
+# Code coverage of python bindings. This has to be below the above brew upgrade
+# and pybind install otherwise those packages get installed for Python 3.6 and
+# then forgotten when 3.7 is installed.
+- if [ "$TRAVIS_OS_NAME" == "linux" ] || [ "$TRAVIS_OS_NAME" == "osx" ]; then pip3 install coverage codecov; fi
+
 # SwiftShader on Linux (cached). Taken from Chromium snapshot 587878
 # (swiftshader-bin Arch package).
 - if [ "$TRAVIS_OS_NAME" == "linux" ] && [ "$TARGET" == "desktop-gles" ] && [ ! -e "$HOME/swiftshader/libEGL.so" ]; then cd $HOME ; wget https://ci.magnum.graphics/swiftshader-chromium-587878.tar.gz && mkdir -p swiftshader && cd swiftshader && tar -xzf ../swiftshader-chromium-587878.tar.gz && cd $TRAVIS_BUILD_DIR ; fi