Fix testing of wheels on macOS.

Author: elprans

.ci/travis-before-install.sh

@@ -43,4 +43,7 @@ if [ "${TRAVIS_OS_NAME}" == "osx" ]; then
     else
         brew install postgresql@${PGVERSION}
     fi
+
+    brew cleanup postgresql@${PGVERSION}
+    brew services start postgresql@${PGVERSION}
 fi

.ci/travis-build-wheels.sh

@@ -56,6 +56,8 @@ if [ "${TRAVIS_OS_NAME}" == "linux" ]; then
     done
 
 elif [ "${TRAVIS_OS_NAME}" == "osx" ]; then
+    export PGINSTALLATION="/usr/local/opt/postgresql@${PGVERSION}/bin"
+
     make clean && make -C "${_root}"
     pip wheel "${_root}" -w "${_root}/dist/"