This patch does three things:
    - disable the libgeos check, because, even setting the proper env variables,
      it fails to load our libgeos library, so we skip that because it's not
      mandatory for the cythonizing.
    - sets some environment variables into the setup.py file, so we can pass
      our libgeos information (includes, lib path and libraries)
    - force to raise an error when cython file to compile (our current build
      system relies on this failure to do the proper `cythonizing`, if we don't
      raise the error, we will end up with the package installed without the
      speed optimizations.
--- Shapely-1.7a1/setup.py.orig	2018-07-29 22:53:13.000000000 +0200
+++ Shapely-1.7a1/setup.py	2019-02-24 14:26:19.178610660 +0100
@@ -82,8 +82,8 @@ if not (py_version == (2, 7) or py_versi

 # Get geos_version from GEOS dynamic library, which depends on
 # GEOS_LIBRARY_PATH and/or GEOS_CONFIG environment variables
-from shapely._buildcfg import geos_version_string, geos_version, \
-        geos_config, get_geos_config
+# from shapely._buildcfg import geos_version_string, geos_version, \
+#         geos_config, get_geos_config

 logging.basicConfig()
 log = logging.getLogger(__file__)
@@ -248,9 +248,9 @@ if sys.platform == 'win32':
     setup_args['package_data']['shapely'].append('shapely/DLLs/*.dll')

 # Prepare build opts and args for the speedups extension module.
-include_dirs = []
-library_dirs = []
-libraries = []
+include_dirs = os.environ.get('GEOS_INCLUDE_DIRS', '').split(',')
+library_dirs = os.environ.get('GEOS_LIBRARY_DIRS', '').split(',')
+libraries = os.environ.get('GEOS_LIBRARIES', '').split(',')
 extra_link_args = []

 # If NO_GEOS_CONFIG is set in the environment, geos-config will not
@@ -375,6 +375,7 @@ try:
         construct_build_ext(existing_build_ext)
     setup(ext_modules=ext_modules, **setup_args)
 except BuildFailed as ex:
+    raise  # Force python only build to fail
     BUILD_EXT_WARNING = "The C extension could not be compiled, " \
                         "speedups are not enabled."
     log.warn(ex)