  The distribution of eccentricities of warm giant exoplanets is commonly
explained through planet--planet interactions, although no physically sound
argument favours the ubiquity of such interactions. No simple, generic
explanation has been put forward to explain the high mean eccentricity of these
planets. In this paper, we revisit a simple, plausible explanation to account
for the eccentricities of warm Jupiters: migration inside a cavity in the
protoplanetary disc. Such a scenario allows to excite the outer eccentric
resonances, a working mechanism for higher mass planets, leading to a growth in
the eccentricity while preventing other, closer resonances to damp
eccentricity. We test this idea with diverse numerical simulations, which show
that the eccentricity of a Jupiter-mass planet around a Sun-like star can
increase up to 0.4, a value never reached before with solely planet--disc
interactions. This high eccentricity is comparable to, if not larger than, the
median eccentricity of warm Saturn- to Jupiter-mass exoplanets. We also discuss
the effects such a mechanism would have on exoplanet observations. This
scenario could have strong consequences on the discs lifetime and the physics
of inner disc dispersal, which could be constrained by the eccentricity
distribution of gas giants.
