Fixed: now we get normal message about hitting unimplemented part of Trager algorithm.

It seems that all current CAS have a problem with this integral:

integrate(1/(-3+v^3)*v/(-4+v^3)^(1/2),v)

   >> Error detected within library code:
   Not integrable (provided residues have no relations)

However, at least the error message could be better...

It seems that the problem is in alglist$PFO, or perhaps in FractionalIdeal. In alglist, the numerator of an ideal is computed, but in the case above, we are dealing with a double fraction, and the result of numer is not a polynomial. On the other hand, it seems that such double fractions are expected. Unfortunately, I have no idea of the mathematics involved.

   >> Error detected within library code:
   (1 . failed) cannot be coerced to mode (SparseUnivariatePolynomial (Expression (Integer)))