integrate constantly asks for "zero or nonzero"

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I've had this problem like several times today, doing integrals of the form

I=1/sqrt(1+(z-z1)^2)
from sage.symbolic.integration.integral import indefinite_integral
indefinite_integral(I,z)

Long error follows, ending with

ValueError: Computation failed since Maxima requested additional constraints; using the 'assume' command before evaluation *may* help (example of legal syntax is 'assume(z1>0)', see `assume?` for more details)
Is z1 zero or nonzero?

So I get that Maxima might want to know if z1 happens to be zero, but unfortunately:

", ".join(map(str, maxima("features")._sage_()))
'integer, noninteger, even, odd, rational, irrational, real, imaginary, complex, analytic, increasing, decreasing, oddfun, evenfun, posfun, constant, commutative, lassociative, rassociative, symmetric, antisymmetric, integervalued'

So how am I supposed to tell Maxima this is "nonzero" if....I can't assume something is nonzero?