Error Running `pip install -r requirements.txt`

console.txt

  Running setup.py install for cffi
    Complete output from command /home/ubuntu/Python_Tasks/env/bin/python -c "import setuptools, tokenize;__file__='/tmp/pip-build-nvVnq5/cffi/setup.py';exec(compile(getattr(tokenize, 'open', open)(__file__).read().replace('\r\n', '\n'), __file__, 'exec'))" install --record /tmp/pip-0rOdqq-record/install-record.txt --single-version-externally-managed --compile --install-headers /home/ubuntu/Python_Tasks/env/include/site/python2.7/cffi:
    running install
    running build
    running build_py
    creating build
    creating build/lib.linux-x86_64-2.7
    creating build/lib.linux-x86_64-2.7/cffi
    copying cffi/__init__.py -> build/lib.linux-x86_64-2.7/cffi
    copying cffi/gc_weakref.py -> build/lib.linux-x86_64-2.7/cffi
    copying cffi/commontypes.py -> build/lib.linux-x86_64-2.7/cffi
    copying cffi/verifier.py -> build/lib.linux-x86_64-2.7/cffi
    copying cffi/backend_ctypes.py -> build/lib.linux-x86_64-2.7/cffi
    copying cffi/vengine_gen.py -> build/lib.linux-x86_64-2.7/cffi
    copying cffi/cparser.py -> build/lib.linux-x86_64-2.7/cffi
    copying cffi/lock.py -> build/lib.linux-x86_64-2.7/cffi
    copying cffi/ffiplatform.py -> build/lib.linux-x86_64-2.7/cffi
    copying cffi/api.py -> build/lib.linux-x86_64-2.7/cffi
    copying cffi/model.py -> build/lib.linux-x86_64-2.7/cffi
    copying cffi/vengine_cpy.py -> build/lib.linux-x86_64-2.7/cffi
    running build_ext
    building '_cffi_backend' extension
    creating build/temp.linux-x86_64-2.7
    creating build/temp.linux-x86_64-2.7/c
    x86_64-linux-gnu-gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -DUSE__THREAD -I/usr/include/ffi -I/usr/include/libffi -I/usr/include/python2.7 -c c/_cffi_backend.c -o build/temp.linux-x86_64-2.7/c/_cffi_backend.o
    c/_cffi_backend.c:13:17: fatal error: ffi.h: No such file or directory
     #include <ffi.h>
                     ^
    compilation terminated.
    error: command 'x86_64-linux-gnu-gcc' failed with exit status 1
    
    ----------------------------------------
    Command "/home/ubuntu/Python_Tasks/env/bin/python -c "import setuptools, tokenize;__file__='/tmp/pip-build-nvVnq5/cffi/setup.py';exec(compile(getattr(tokenize, 'open', open)(__file__).read().replace('\r\n', '\n'), __file__, 'exec'))" install --record /tmp/pip-0rOdqq-record/install-record.txt --single-version-externally-managed --compile --install-headers /home/ubuntu/Python_Tasks/env/include/site/python2.7/cffi" failed with error code 1 in /tmp/pip-build-nvVnq5/cffi