Setup jsdelvr-bot for testing proposes on Heroku?

[ghost]

How can I setup the jsdelvr-bot for testing proposes on Heroku?

I get this following warning:

-----> Python app detected
-----> Installing python-2.7.11
     $ pip install -r requirements.txt
       Collecting PyYAML>=3 (from -r requirements.txt (line 1))
         Downloading PyYAML-3.11.zip (371kB)
       Collecting Twisted==13.1.0 (from -r requirements.txt (line 2))
         Downloading Twisted-13.1.0.tar.bz2 (2.7MB)
       Collecting async==0.6.1 (from -r requirements.txt (line 3))
         Downloading async-0.6.1.tar.gz
       Collecting blinker==1.3 (from -r requirements.txt (line 4))
         Downloading blinker-1.3.tar.gz (91kB)
       Collecting github3.py==0.9.3 (from -r requirements.txt (line 5))
         Downloading github3.py-0.9.3-py2.py3-none-any.whl (104kB)
       Collecting pystache==0.5 (from -r requirements.txt (line 6))
         Downloading pystache-0.5.0.tar.gz
       Collecting requests>=2.2 (from -r requirements.txt (line 7))
         Downloading requests-2.10.0-py2.py3-none-any.whl (506kB)
       Collecting semantic-version==2.3 (from -r requirements.txt (line 8))
         Downloading semantic_version-2.3.0.tar.gz
       Collecting pyopenssl>=0.15.1 (from -r requirements.txt (line 9))
         Downloading pyOpenSSL-16.0.0-py2.py3-none-any.whl (45kB)
       Collecting ndg-httpsclient>=0.4.0 (from -r requirements.txt (line 10))
         Downloading ndg_httpsclient-0.4.0.tar.gz
       Collecting pyasn1>=0.1.9 (from -r requirements.txt (line 11))
         Downloading pyasn1-0.1.9-py2.py3-none-any.whl
       Collecting zope.interface>=3.6.0 (from Twisted==13.1.0->-r requirements.txt (line 2))
         Downloading zope.interface-4.1.3.tar.gz (141kB)
       Collecting uritemplate.py>=0.2.0 (from github3.py==0.9.3->-r requirements.txt (line 5))
         Downloading uritemplate.py-0.3.0.tar.gz
       Collecting cryptography>=1.3 (from pyopenssl>=0.15.1->-r requirements.txt (line 9))
         Downloading cryptography-1.4.tar.gz (399kB)
       Collecting six>=1.5.2 (from pyopenssl>=0.15.1->-r requirements.txt (line 9))
         Downloading six-1.10.0-py2.py3-none-any.whl
       Collecting idna>=2.0 (from cryptography>=1.3->pyopenssl>=0.15.1->-r requirements.txt (line 9))
         Downloading idna-2.1-py2.py3-none-any.whl (54kB)
       Collecting enum34 (from cryptography>=1.3->pyopenssl>=0.15.1->-r requirements.txt (line 9))
         Downloading enum34-1.1.6-py2-none-any.whl
       Collecting ipaddress (from cryptography>=1.3->pyopenssl>=0.15.1->-r requirements.txt (line 9))
         Downloading ipaddress-1.0.16-py27-none-any.whl
       Collecting cffi>=1.4.1 (from cryptography>=1.3->pyopenssl>=0.15.1->-r requirements.txt (line 9))
         Downloading cffi-1.6.0.tar.gz (397kB)
       Collecting pycparser (from cffi>=1.4.1->cryptography>=1.3->pyopenssl>=0.15.1->-r requirements.txt (line 9))
         Downloading pycparser-2.14.tar.gz (223kB)
       Installing collected packages: PyYAML, zope.interface, Twisted, async, blinker, requests, uritemplate.py, github3.py, pystache, semantic-version, idna, pyasn1, six, enum34, ipaddress, pycparser, cffi, cryptography, pyopenssl, ndg-httpsclient
         Running setup.py install for PyYAML: started
           Running setup.py install for PyYAML: finished with status 'done'
         Running setup.py install for zope.interface: started
           Running setup.py install for zope.interface: finished with status 'done'
         Running setup.py install for Twisted: started
           Running setup.py install for Twisted: finished with status 'done'
         Running setup.py install for async: started
           Running setup.py install for async: finished with status 'done'
         Running setup.py install for blinker: started
           Running setup.py install for blinker: finished with status 'done'
         Running setup.py install for uritemplate.py: started
           Running setup.py install for uritemplate.py: finished with status 'done'
         Running setup.py install for pystache: started
           Running setup.py install for pystache: finished with status 'done'
         Running setup.py install for semantic-version: started
           Running setup.py install for semantic-version: finished with status 'done'
         Running setup.py install for pycparser: started
           Running setup.py install for pycparser: finished with status 'done'
         Running setup.py install for cffi: started
           Running setup.py install for cffi: finished with status 'error'
           Complete output from command /app/.heroku/python/bin/python -u -c "import setuptools, tokenize;__file__='/tmp/pip-build-eFKfun/cffi/setup.py';exec(compile(getattr(tokenize, 'open', open)(__file__).read().replace('\r\n', '\n'), __file__, 'exec'))" install --record /tmp/pip-ZFAHUC-record/install-record.txt --single-version-externally-managed --compile:
           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 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 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
           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/cparser.py -> build/lib.linux-x86_64-2.7/cffi
           copying cffi/backend_ctypes.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/setuptools_ext.py -> build/lib.linux-x86_64-2.7/cffi
           copying cffi/vengine_cpy.py -> build/lib.linux-x86_64-2.7/cffi
           copying cffi/verifier.py -> build/lib.linux-x86_64-2.7/cffi
           copying cffi/ffiplatform.py -> build/lib.linux-x86_64-2.7/cffi
           copying cffi/model.py -> build/lib.linux-x86_64-2.7/cffi
           copying cffi/recompiler.py -> build/lib.linux-x86_64-2.7/cffi
           copying cffi/lock.py -> build/lib.linux-x86_64-2.7/cffi
           copying cffi/api.py -> build/lib.linux-x86_64-2.7/cffi
           copying cffi/cffi_opcode.py -> build/lib.linux-x86_64-2.7/cffi
           copying cffi/vengine_gen.py -> build/lib.linux-x86_64-2.7/cffi
           copying cffi/_cffi_include.h -> build/lib.linux-x86_64-2.7/cffi
           copying cffi/parse_c_type.h -> build/lib.linux-x86_64-2.7/cffi
           copying cffi/_embedding.h -> 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
           gcc -pthread -fno-strict-aliasing -g -O2 -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -fPIC -DUSE__THREAD -I/usr/include/ffi -I/usr/include/libffi -I/app/.heroku/python/include/python2.7 -c c/_cffi_backend.c -o build/temp.linux-x86_64-2.7/c/_cffi_backend.o
           c/_cffi_backend.c:15:17: fatal error: ffi.h: No such file or directory
            #include <ffi.h>
                            ^
           compilation terminated.
           error: command 'gcc' failed with exit status 1

           ----------------------------------------
       Command "/app/.heroku/python/bin/python -u -c "import setuptools, tokenize;__file__='/tmp/pip-build-eFKfun/cffi/setup.py';exec(compile(getattr(tokenize, 'open', open)(__file__).read().replace('\r\n', '\n'), __file__, 'exec'))" install --record /tmp/pip-ZFAHUC-record/install-record.txt --single-version-externally-managed --compile" failed with error code 1 in /tmp/pip-build-eFKfun/cffi/
 !     Push rejected, failed to compile Python app