fix warning about renamed method in django 1.8

[jschneier]

@yakky

[spil-rkoopmans]

Can we get this merged?

[stefanfoulis]

@spil-rkoopmans thanks for the patch :-)
Could you add comments in the code so we know why this try/except exists? Especially for which Django versions it is.

[stefanfoulis]

Sorry, I meant @jschneier

[jschneier]

@stefanfoulis done and force pushed. Just want to confirm that filer is still supporting 1.4/1.5? If not then I can just rename the method and remove the workaround.

[yakky]

Thanks @jschneier !