It seems as recent versions of `trezor` don't work with python 2.x:
```
/build/trezor-0.9.1/dist /build/trezor-0.9.1
Processing ./trezor-0.9.1-py2-none-any.whl
trezor requires Python '>=3.3' but the running Python is 2.7.15
builder for '/nix/store/aqyxki0ckanjk4r1f0an4kj1w4s3kk4f-python2.7-trezor-0.9.1.drv' failed with exit code 1
cannot build derivation '/nix/store/gp4smkzc9r87lzajs17jnq4rh2ayc5q0-python2.7-keepkey-4.0.0.drv': 1 dependencies couldn't be built
```
The package is currently broken and most folks recommend to use
`flask-caching` (see
https://github.com/thadeusb/flask-cache/issues/171).
The only package in `nixpkgs` which remained to use `flask_cache`
(`graphite_api`) still builds with `pythonPackages.flask-caching`.
The removal and corresponding `graphite_api` change unbreaks several
Hydra builds (see https://hydra.nixos.org/build/76953777).
tdesktopPackages.preview: 1.3.7 -> 1.3.10
Without the patch the build will fail with the following error:
[ 15%] Building CXX object CMakeFiles/lib_export.dir/build/tdesktop/Telegram/SourceFiles/export/export_api_wrap.o
/build/tdesktop/Telegram/SourceFiles/export/export_api_wrap.cpp: In lambda function:
/build/tdesktop/Telegram/SourceFiles/export/export_api_wrap.cpp:712:56: internal compiler error: Segmentation fault
if constexpr (MTPDphotos_photos::Is<decltype(data)>()) {
^
Please submit a full bug report,
with preprocessed source if appropriate.
See <https://gcc.gnu.org/bugs/> for instructions.
make[2]: *** [CMakeFiles/lib_export.dir/build.make:77: CMakeFiles/lib_export.dir/build/tdesktop/Telegram/SourceFiles/export/export_api_wrap.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:1101: CMakeFiles/lib_export.dir/all] Error 2
make: *** [Makefile:84: all] Error 2
Problem: Restarting (stopping) system.slice would not only stop X11 but
also most system units/services. We obviously don't want this happening
to users when they switch from 18.03 to 18.09 or nixos-unstable.
Reason: The following change in systemd:
d8e5a93382
The commit adds system.slice to the perpetual units, which means
removing the unit file and adding it to the source code. This is done so
that system.slice can't be stopped anymore but in our case it ironically
would cause this script to stop system.slice because the unit file was
removed (and an older systemd version is still running).
Related issue: https://github.com/NixOS/nixpkgs/issues/39791
