  Tests of the no-hair theorem using astrophysical black holes involve the
detection of at least two quasi-normal modes (QNMs) in the gravitational wave
emitted by a perturbed black hole. A detection of two modes -- the dominant,
$(\ell, m, n) = (2,2,0)$, mode and its first overtone, the $(2,2,1)$ mode -- in
the post-merger signal of the binary black hole merger GW150914 was claimed in
Isi et al. [arXiv:1905.00869], with further evidence provided in Isi & Farr
[arXiv:2202.02941]. However, Cotesta et al. [arXiv:2201.00822] disputed this
claim, finding that evidence for the overtone only appeared if the signal was
analyzed before merger, when a QNM description of the signal is not valid. Due
to technical challenges, both of these analyses fixed the merger time and sky
location of GW150914 when estimating the evidence for the overtone. At least
some of the contention can be attributed to fixing these parameters. Here, we
surmount this difficulty and fully marginalize over merger time and
sky-location uncertainty while doing a post-merger QNM analysis of GW150914. We
find that marginalizing over all parameters yields low evidence for the
presence of the overtone, with a Bayes factor of $1.10\pm 0.03$ in favor of a
QNM model with the overtone versus one without. The arrival time uncertainty of
GW150914 is too large to definitively claim detection of the $(2,2,1)$ mode.
