Throw warning on missing CSS rather than error, so that tests can still run on Dj1.7
Throw warning on missing CSS rather than error, so that tests can still run on Dj1.7

iansprice/wagtail,quru/wagtail,inonit/wagtail,takeflight/wagtail,mixxorz/wagtail,nilnvoid/wagtail,kurtrwall/wagtail,JoshBarr/wagtail,hamsterbacke23/wagtail,kaedroho/wagtail,gasman/wagtail,FlipperPA/wagtail,nilnvoid/wagtail,rsalmaso/wagtail,jnns/wagtail,FlipperPA/wagtail,nealtodd/wagtail,nealtodd/wagtail,iansprice/wagtail,thenewguy/wagtail,mikedingjan/wagtail,thenewguy/wagtail,kaedroho/wagtail,nimasmi/wagtail,gogobook/wagtail,mikedingjan/wagtail,JoshBarr/wagtail,kaedroho/wagtail,kurtrwall/wagtail,zerolab/wagtail,nimasmi/wagtail,mixxorz/wagtail,hamsterbacke23/wagtail,inonit/wagtail,inonit/wagtail,rsalmaso/wagtail,gasman/wagtail,wagtail/wagtail,wagtail/wagtail,mixxorz/wagtail,mixxorz/wagtail,Toshakins/wagtail,quru/wagtail,FlipperPA/wagtail,Toshakins/wagtail,gogobook/wagtail,takeflight/wagtail,gasman/wagtail,hamsterbacke23/wagtail,Toshakins/wagtail,nilnvoid/wagtail,kaedroho/wagtail,chrxr/wagtail,nutztherookie/wagtail,inonit/wagtail,nutztherookie/wagtail,timorieber/wagtail,quru/wagtail,kurtw/wagtail,torchbox/wagtail,zerolab/wagtail,timorieber/wagtail,rsalmaso/wagtail,takeflight/wagtail,nimasmi/wagtail,thenewguy/wagtail,takeflight/wagtail,jnns/wagtail,torchbox/wagtail,hamsterbacke23/wagtail,gogobook/wagtail,kurtrwall/wagtail,jnns/wagtail,rsalmaso/wagtail,quru/wagtail,kurtw/wagtail,timorieber/wagtail,Toshakins/wagtail,iansprice/wagtail,JoshBarr/wagtail,davecranwell/wagtail,nealtodd/wagtail,kurtrwall/wagtail,wagtail/wagtail,gasman/wagtail,davecranwell/wagtail,nimasmi/wagtail,FlipperPA/wagtail,nutztherookie/wagtail,iansprice/wagtail,nilnvoid/wagtail,thenewguy/wagtail,kurtw/wagtail,thenewguy/wagtail,mikedingjan/wagtail,chrxr/wagtail,torchbox/wagtail,nealtodd/wagtail,zerolab/wagtail,gogobook/wagtail,wagtail/wagtail,torchbox/wagtail,zerolab/wagtail,mikedingjan/wagtail,zerolab/wagtail,davecranwell/wagtail,kaedroho/wagtail,kurtw/wagtail,rsalmaso/wagtail,chrxr/wagtail,gasman/wagtail,wagtail/wagtail,JoshBarr/wagtail,nutztherookie/wagtail,mixxorz/wagtail,davecranwell/wagtail,chrxr/wagtail,timorieber/wagtail,jnns/wagtail