Unable to start QEPCAD

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I have compiled and installed qepcad-1.50, but I can't run it. For example, these are lifted from the documentation:

sage: var('a,b,c,d,x,y,z')
sage: qf = qepcad_formula
sage: ellipse = 3*x^2 + 2*x*y + y^2 - x + y - 7
sage: F = qf.exists(y, ellipse == 0)
sage: qepcad(F)

However, this produces an error:

RuntimeError: Unable to start QEPCAD

I did discover a patch at https://abf.rosalinux.ru/import/sagem... but I'm not sure how to apply it. I'd be very happy for some advice.

I'm running sage-6.2, under Ubuntu 14.04.