$ make -j4
  CXX      src/core/libvapoursynth_la-vscore.lo
  CXX      src/core/libvapoursynth_la-vsresize.lo
  CXX      src/core/libexprfilter_la-exprfilter.lo
  CXX      src/vsscript/libvapoursynth_script_la-vsscript.lo
  CC       src/filters/eedi3/libeedi3_la-eedi3.lo
  CXX      src/filters/misc/libmiscfilters_la-miscfilters.lo
  CC       src/filters/morpho/libmorpho_la-morpho.lo
  CC       src/filters/morpho/libmorpho_la-morpho_filters.lo
  CC       src/filters/morpho/libmorpho_la-morpho_selems.lo
  CXX      src/filters/removegrain/libremovegrain_la-clense.lo
  CXX      src/filters/removegrain/libremovegrain_la-removegrainvs.lo
  CXX      src/filters/removegrain/libremovegrain_la-repairvs.lo
  CXX      src/filters/removegrain/libremovegrain_la-shared.lo
  CXX      src/filters/removegrain/libremovegrain_la-verticalcleaner.lo
  CC       src/filters/vinverse/libvinverse_la-vinverse.lo
  CC       src/filters/vivtc/libvivtc_la-vivtc.lo
  CYTHON   src/cython/vapoursynth.c

Error compiling Cython file:
------------------------------------------------------------
...
        # If we are not using VSScript, do nothing.
        if self.single:
            return
        _environment_state.current = _env_current_stack().pop()

    def __eq__(self, other):
   ^
------------------------------------------------------------

src/cython/vapoursynth.pyx:133:4: Special method __eq__ must be implemented via __richcmp__

Error compiling Cython file:
------------------------------------------------------------
...
        core = kwargs.pop("core", None) or get_core()
        vals = self._as_dict()
        vals.update(**kwargs)
        return core.register_format(**vals)

    def __eq__(self, other):
   ^
------------------------------------------------------------

src/cython/vapoursynth.pyx:710:4: Special method __eq__ must be implemented via __richcmp__
  CXX      src/vspipe/vspipe.o
Makefile:2018: recipe for target 'src/cython/vapoursynth.c' failed
make: *** [src/cython/vapoursynth.c] Error 1
make: *** Waiting for unfinished jobs....