Thanks again! I've made the changes, so here's another set of patches.
Note that the second patch is unchanged, just rebased.

On Wed, 25 Apr 2018 15:40:34 +0200
Marius Bakke <mbakke@fastmail.com> wrote:

> Rutger Helling <rhelling@mykolab.com> writes:
> 
> > Hello Marius, 
> >
> > Thanks for the review! I've taken your suggestions into account and
> > updated the patches.
> >
> > I don't think it's possible to seperate the GTK3 frontend, since
> > it's just a parameter you pass to the qemu* binaries (-display gtk
> > instead of -display sdl).
> >
> > From my understanding if you have both GTK3 and SDL2 enabled it
> > defaults to GTK3. We can remove the SDL2 frontend if there are no
> > objections (and probably sdl from the --audio-drv-list). I just
> > figured it'd be nicer to enable both to give users maximum
> > flexibility.  
> 
> OK!
> 
> [...]
> 
> > From e1b40133c8aedf84090fbd4292af2b53eb22d669 Mon Sep 17 00:00:00
> > 2001 From: Rutger Helling <rhelling@mykolab.com>
> > Date: Wed, 25 Apr 2018 14:59:11 +0200
> > Subject: [PATCH 1/2] gnu: qemu: Build with Python 3 and SDL2
> > support.
> >
> > * gnu/packages/bootloaders.scm (qemu-minimal-2.10): Remove variable.
> > * gnu/packages/virtualization.scm (qemu)[inputs]: Use sdl2 instead
> > of sdl. [native-inputs]: Use python instead of python@2. Add
> > python-wrapper.
> > * gnu/packages/virtualization.scm (qemu-minimal)[inputs]: Remove
> > sdl2 instead of sdl from inherited packages.
> > * gnu/packages/virtualization.scm (qemu-minimal-2.10): Add variable.
> > [native-inputs]: Remove python from inherited packages and use
> > python@2 instead. ---
> >  gnu/packages/bootloaders.scm    | 16 ----------------
> >  gnu/packages/virtualization.scm | 30 ++++++++++++++++++++++++++----
> >  2 files changed, 26 insertions(+), 20 deletions(-)  
> 
> Can you adjust 'american-fuzzy-lop' to use the moved qemu-minimal-2.10
> package too?  Please also drop the '@@ (gnu packages bootloaders)'
> stuff and just use '(inherit qemu-minimal-2.10 ...)' now that it's
> public.
> 
> [...]
> 
> > @@ -187,7 +187,7 @@ exec smbd $@")))
> >         ;; ("pciutils" ,pciutils)
> >         ("pixman" ,pixman)
> >         ("pulseaudio" ,pulseaudio)
> > -       ("sdl" ,sdl)
> > +       ("sdl2" ,sdl2)
> >         ("spice" ,spice)
> >         ("usbredir" ,usbredir)
> >         ("util-linux" ,util-linux)
> > @@ -197,7 +197,8 @@ exec smbd $@")))
> >      (native-inputs `(("glib:bin" ,glib "bin") ; gtester, etc.
> >                       ("perl" ,perl)
> >                       ("pkg-config" ,pkg-config)
> > -                     ("python" ,python-2) ; incompatible with
> > Python 3 according to error message
> > +                     ("python" ,python)
> > +                     ("python-wrapper" ,python-wrapper)  
> 
> The first "python" can be removed (only python-wrapper is necessary).
> 
> >                       ("texinfo" ,texinfo)))
> >      (home-page "https://www.qemu.org")
> >      (synopsis "Machine emulator and virtualizer")
> > @@ -233,9 +234,30 @@ server and embedded PowerPC, and S390 guests.")
> >  
> >      ;; Remove dependencies on optional libraries, notably GUI
> > libraries. (inputs (fold alist-delete (package-inputs qemu)
> > -                  '("libusb" "mesa" "sdl" "spice" "virglrenderer"
> > +                  '("libusb" "mesa" "sdl2" "spice" "virglrenderer"
> >                      "usbredir" "libdrm" "libepoxy"
> > "pulseaudio"))))) 
> > +;; The GRUB test suite fails with later versions of Qemu, so we
> > +;; keep it at 2.10 for now.  See
> > +;;
> > <https://lists.gnu.org/archive/html/bug-grub/2018-02/msg00004.html>.
> > +;; TODO: When grub no longer needs this version, move to
> > gnu/packages/debug.scm.  
> 
> The TODO line can be removed too.  And maybe add a comment such as
> "Keep it hidden since we don't backport security patches" or
> something along those lines.
> 
> [...]
> 
> > From edea64c09dc1e0f391e860478dcf99f4d0d1a6d2 Mon Sep 17 00:00:00
> > 2001 From: Rutger Helling <rhelling@mykolab.com>
> > Date: Wed, 25 Apr 2018 15:03:29 +0200
> > Subject: [PATCH 2/2] gnu: qemu: Enable GTK3 frontend.
> >
> > * gnu/packages/virtualization.scm (qemu)[native-inputs]: Add
> > "gettext" to native-inputs. [inputs]: Add "gtk+" to inputs.
> > * gnu/packages/virtualization.scm (qemu-minimal)[native-inputs]:
> > Remove "gettext" from inherited inputs.
> > [inputs]: Remove "gtk+" from inherited inputs.  
> 
> LGTM!