How to use freqz to get response of complex FIR filter
Never mind, it is absolutely possible to pass a set of complex coefficients to freqz, I got confused because I tried to plot the response without specifying I wanted the absolute value of h, which rendered the warning: 
ComplexWarning: Casting complex values to real discards the imaginary part. Trap for young players like myself!
I'm trying to analyse an asymmetric FIR filter with complex coefficients. I know I can use the numpy function freqz to analyse the frequency response of an FIR or IIR-filter with real coefficients. At the moment I'm just using a regular FFT of the FIR filter and I use fftshift to put the negative frequencies in front of 0 and then I do fftfreqs to calculate the frequency bins and finally, I add the carrier frequency to all the frequencies in the array which is given by fftfreqs. Anyway, I'm pretty sure that that's the wrong way.