我尝试在我的树莓派上安装 python-telegram-bot 但遇到了这个问题：
Complete output from command /usr/bin/python -u -c "import setuptools, tokenize;__file__='/tmp/pip-build-QLuRQr/cffi/setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" install --record /tmp/pip-1vjudm-record/install-record.txt --single-version-externally-managed --compile --user --prefix=:
Package libffi was not found in the pkg-config search path.
Perhaps you should add the directory containing `libffi.pc'
to the PKG_CONFIG_PATH environment variable
No package 'libffi' found
Package libffi was not found in the pkg-config search path.
Perhaps you should add the directory containing `libffi.pc'
to the PKG_CONFIG_PATH environment variable
No package 'libffi' found
Package …