One extra forward slash (/) in front of tx and the *.xml file troubled me for 8 hours!!
My mistake:
http://www.springframework.org/schema/tx/ http://www.springframework.org/schema/tx/spring-tx-4.3.xsd
Correction:
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.3.xsd
Indeed one character less/more manages to keep programmers busy for hours!