test_travis.sh: don't attempt to create an empty directory twice
test_travis.sh: don't attempt to create an empty directory twice

lindsayad/sympy,hargup/sympy,yashsharan/sympy,hargup/sympy,mafiya69/sympy,drufat/sympy,postvakje/sympy,Curious72/sympy,aktech/sympy,Curious72/sympy,skidzo/sympy,rahuldan/sympy,kaushik94/sympy,jaimahajan1997/sympy,drufat/sympy,kaichogami/sympy,Titan-C/sympy,skidzo/sympy,ChristinaZografou/sympy,madan96/sympy,chaffra/sympy,Curious72/sympy,chaffra/sympy,sampadsaha5/sympy,sampadsaha5/sympy,drufat/sympy,mafiya69/sympy,madan96/sympy,aktech/sympy,mafiya69/sympy,sampadsaha5/sympy,jerli/sympy,skidzo/sympy,jaimahajan1997/sympy,postvakje/sympy,souravsingh/sympy,rahuldan/sympy,Titan-C/sympy,jerli/sympy,ChristinaZografou/sympy,jaimahajan1997/sympy,lindsayad/sympy,kaichogami/sympy,aktech/sympy,souravsingh/sympy,lindsayad/sympy,Titan-C/sympy,yashsharan/sympy,kaichogami/sympy,jerli/sympy,yashsharan/sympy,postvakje/sympy,souravsingh/sympy,hargup/sympy,ChristinaZografou/sympy,kaushik94/sympy,chaffra/sympy,madan96/sympy,rahuldan/sympy,kaushik94/sympy