Improve error message when using pytest.skip at module level
Improve error message when using pytest.skip at module level

As discussed in issue #1959.
jaraco/pytest,ddboline/pytest,nicoddemus/pytest,eli-b/pytest,alfredodeza/pytest,hackebrot/pytest,davidszotten/pytest,rmfitzpatrick/pytest,hpk42/pytest,RonnyPfannschmidt/pytest,pytest-dev/pytest,malinoff/pytest,skylarjhdownes/pytest,markshao/pytest,The-Compiler/pytest,vmalloc/dessert,flub/pytest,tomviner/pytest,pfctdayelise/pytest,MichaelAquilina/pytest,tomviner/pytest,The-Compiler/pytest,tgoodlet/pytest,hpk42/pytest,tareqalayan/pytest,txomon/pytest,nicoddemus/pytest,etataurov/pytest,Akasurde/pytest