Jenkinsfile: install pytest-html package for generating html test report.

Jenkinsfile

@@ -21,6 +21,7 @@ pipeline {
                 echo 'Testing..'
 		sh 'sudo docker run -d -p 4444:4444 selenium/standalone-chrome'
 		sh 'pip3 install pytest -U -q'
+		sh 'pip3 install pytest-html -U -q'		
 		sh 'pip3 install selenium -U -q'
 		sh 'pytest -v -s --html=EnglishPalTestReport.html ./app/test'
             }