pitivi fails to build with Python 3.9.0a2.

+ /usr/bin/ninja -v -j2 -C x86_64-redhat-linux-gnu
ninja: Entering directory `x86_64-redhat-linux-gnu'
[1/4] cc -Irenderer@sha -I. -I.. -I/usr/include/gstreamer-1.0 -I/usr/include/glib-2.0 -I/usr/lib64/glib-2.0/include -I/usr/include/python3.9 -I/usr/include/pycairo -I/usr/include/cairo -I/usr/include/pixman-1 -I/usr/include/freetype2 -I/usr/include/libpng16 -fdiagnostics-color=always -pipe -D_FILE_OFFSET_BITS=64 -O2 -g -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS -fexceptions -fstack-protector-strong -grecord-gcc-switches -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -m64 -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection -fPIC -pthread -MD -MQ 'renderer@sha/pitivi_coptimizations_renderer.c.o' -MF 'renderer@sha/pitivi_coptimizations_renderer.c.o.d' -o 'renderer@sha/pitivi_coptimizations_renderer.c.o' -c ../pitivi/coptimizations/renderer.c
[2/4] /usr/bin/intltool-merge --desktop-style /builddir/build/BUILD/pitivi-0.999/po ../data/org.pitivi.Pitivi.desktop.in data/org.pitivi.Pitivi.desktop
Merging translations into data/org.pitivi.Pitivi.desktop.
[3/4] cc  -o renderer.so 'renderer@sha/pitivi_coptimizations_renderer.c.o' -Wl,--as-needed -Wl,--no-undefined -shared -fPIC -Wl,--start-group -Wl,-soname,renderer.so -O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS -fexceptions -fstack-protector-strong -grecord-gcc-switches -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -m64 -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection -Wl,-z,relro -Wl,--as-needed -Wl,-z,now -specs=/usr/lib/rpm/redhat/redhat-hardened-ld /usr/lib64/libgstreamer-1.0.so /usr/lib64/libgobject-2.0.so /usr/lib64/libglib-2.0.so /usr/lib64/libcairo.so -Wl,--end-group
FAILED: renderer.so 
cc  -o renderer.so 'renderer@sha/pitivi_coptimizations_renderer.c.o' -Wl,--as-needed -Wl,--no-undefined -shared -fPIC -Wl,--start-group -Wl,-soname,renderer.so -O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS -fexceptions -fstack-protector-strong -grecord-gcc-switches -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -m64 -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection -Wl,-z,relro -Wl,--as-needed -Wl,-z,now -specs=/usr/lib/rpm/redhat/redhat-hardened-ld /usr/lib64/libgstreamer-1.0.so /usr/lib64/libgobject-2.0.so /usr/lib64/libglib-2.0.so /usr/lib64/libcairo.so -Wl,--end-group
/usr/bin/ld: renderer@sha/pitivi_coptimizations_renderer.c.o: in function `py_fill_surface':
/builddir/build/BUILD/pitivi-0.999/x86_64-redhat-linux-gnu/../pitivi/coptimizations/renderer.c:30: undefined reference to `PyList_Type'
/usr/bin/ld: /builddir/build/BUILD/pitivi-0.999/x86_64-redhat-linux-gnu/../pitivi/coptimizations/renderer.c:30: undefined reference to `PyArg_ParseTuple'
/usr/bin/ld: /builddir/build/BUILD/pitivi-0.999/x86_64-redhat-linux-gnu/../pitivi/coptimizations/renderer.c:33: undefined reference to `PyList_Size'
/usr/bin/ld: /builddir/build/BUILD/pitivi-0.999/x86_64-redhat-linux-gnu/../pitivi/coptimizations/renderer.c:50: undefined reference to `PyList_GetItem'
/usr/bin/ld: /builddir/build/BUILD/pitivi-0.999/x86_64-redhat-linux-gnu/../pitivi/coptimizations/renderer.c:51: undefined reference to `PyFloat_AsDouble'
/usr/bin/ld: /builddir/build/BUILD/pitivi-0.999/x86_64-redhat-linux-gnu/../pitivi/coptimizations/renderer.c:54: undefined reference to `PyErr_Occurred'
/usr/bin/ld: renderer@sha/pitivi_coptimizations_renderer.c.o: in function `_Py_DECREF':
/usr/include/python3.9/object.h:478: undefined reference to `_Py_Dealloc'
/usr/bin/ld: /usr/include/python3.9/object.h:478: undefined reference to `_Py_Dealloc'
/usr/bin/ld: renderer@sha/pitivi_coptimizations_renderer.c.o: in function `import_cairo':
/usr/include/pycairo/py3cairo.h:270: undefined reference to `PyCapsule_Import'
/usr/bin/ld: renderer@sha/pitivi_coptimizations_renderer.c.o: in function `PyInit_renderer':
/builddir/build/BUILD/pitivi-0.999/x86_64-redhat-linux-gnu/../pitivi/coptimizations/renderer.c:134: undefined reference to `PyModule_Create2'
collect2: error: ld returned 1 exit status
[4/4] /usr/bin/intltool-merge --xml-style /builddir/build/BUILD/pitivi-0.999/po ../data/org.pitivi.Pitivi.appdata.xml.in data/org.pitivi.Pitivi.appdata.xml
Merging translations into data/org.pitivi.Pitivi.appdata.xml.
CREATED data/org.pitivi.Pitivi.appdata.xml
ninja: build stopped: subcommand failed.


Seems like ninja does not find the 3.9 version of Python and forgets to link with it. But the problem might be different.

For the build logs, see:
https://copr-be.cloud.fedoraproject.org/results/@python/python3.9/fedora-rawhide-x86_64/01145585-pitivi/

For all our attempts to build pitivi with Python 3.9, see:
https://copr.fedorainfracloud.org/coprs/g/python/python3.9/package/pitivi/

Testing and mass rebuild of packages is happening in copr. You can follow these instructions to test locally in mock if your package builds with Python 3.9:
https://copr.fedorainfracloud.org/coprs/g/python/python3.9/

Let us know here if you have any questions.

Python 3.9 will be included in Fedora 33. To make that update smoother, we're building Fedora packages with early pre-releases of Python 3.9.
A build failure prevents us from testing all dependent packages (transitive [Build]Requires), so it's important for us to get it fixed soon.
We'd appreciate help from the people who know this package best, but if you don't want to work on this now, let us know so we can try to work around it on our side.