  With the installation of a new 28-m diameter imaging atmospheric Cherenkov
telescope in the middle of the array, the H.E.S.S. instrument has entered since
2012 into its Phase II. The fifth large-size telescope is particularly
important to lower the threshold energy of the array, and is thus a unique
instrument to observe low-frequency-peaked blazars, such as flat-spectrum
radio-quasars (FSRQs), which remain rare in the very-high- energy (VHE; E $>$
100 GeV) $\gamma$-ray domain. In this contribution, we report on the discovery
with the H.E.S.S. telescopes of VHE $\gamma$-ray emission from the FSRQ PKS
0736+017 (z=0.189). H.E.S.S. observations were triggered as a
target-of-opportunity in February 2015 following the detection of $\gamma$-ray
flaring activity in the MeV-GeV energy-band with Fermi-LAT. Significant VHE
emission is detected with H.E.S.S. only during one of the nights of the
observing campaign, showing at least night-by-night variability in the VHE
regime. We discuss the location of the $\gamma$-ray emitting region within the
relativistic jet, using opacity and variability constraints.
