MAINT: fix issue with Travis CI run.
MAINT: fix issue with Travis CI run.

PyWavelets/pywt,michelp/pywt,rgommers/pywt,PyWavelets/pywt,michelp/pywt,kwohlfahrt/pywt,aaren/pywt,aaren/pywt,kwohlfahrt/pywt,rgommers/pywt,michelp/pywt,rgommers/pywt,aaren/pywt,Dapid/pywt,grlee77/pywt,rgommers/pywt,ThomasA/pywt,Dapid/pywt,grlee77/pywt,ThomasA/pywt,eriol/pywt,Dapid/pywt,ThomasA/pywt,kwohlfahrt/pywt,eriol/pywt,eriol/pywt