Colcon Build error using Cython in setup.py [closed]

edit

Hi,
I'm using ROS2 Eloquent on Ubuntu 18.04 and im trying to use from Cython.Build import cythonize in my setup.py.
My package contains the file cythontest.pyx and the first time i launch colcon build i get an error but the correspronding cythontest.c is created in the same directory. When launching colcon build again and the error is gone and i can launch my node with the method from cythontest.pyx. But if the cythontest.c gets deleted the same pattern occurs again.
To clarify I tested this file outside of the ros2 envoriment and it works fine.

My setup.py

from setuptools import setup, find_packages
from Cython.Build import cythonize

package_name = 'object_detector'

setup(
    ext_modules=cythonize("object_detector/cythontest.pyx"),
    name=package_name,
    version='0.0.0',
    packages=find_packages(exclude=['test']),
    data_files=[
        ('share/ament_index/resource_index/packages',
            ['resource/' + package_name]),
        ('share/' + package_name, ['package.xml']),
    ],
    install_requires=['setuptools', "wheel", "Cython"],
    zip_safe=True,
    maintainer='simon',
    maintainer_email='...',
    description='TODO: Package description',
    license='TODO: License declaration',
    tests_require=['pytest'],
    entry_points={
        'console_scripts': [
            'object_detection = object_detector.object_detection:main'
        ],
    },
)

The following error occurs

colcon build
Starting >>> detection_data
Starting >>> realsense2_camera_msgs
Starting >>> camera_calibration
Starting >>> realsense2_description
Finished <<< realsense2_description [0.95s]                              
Finished <<< camera_calibration [1.35s]                                   
Finished <<< realsense2_camera_msgs [1.59s]                               
Starting >>> realsense2_camera
Finished <<< detection_data [1.65s]
Starting >>> object_detector
/home/simon/.local/lib/python3.6/site-packages/Cython/Compiler/Main.py:369: FutureWarning: Cython directive 'language_level' not set, using 2 for now (Py2). This will change in a later release! File: /home/simon/sciebo/Uni/7_Semester/Bachelor_Arbeit/IS_Bachelor_Arbeit/Bachelor_Thesis/Datentraeger_Dateien/Software/IS/dev_ws/src/object_detector/object_detector/cythontest.pyx
  tree = Parsing.p_module(s, pxd, full_module_name)
--- stderr: object_detector                                                
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/colcon_core/executor/__init__.py", line 91, in __call__
    rc = await self.task(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/colcon_core/task/__init__.py", line 93, in __call__
    return await task_method(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/colcon_ros/task/ament_python/build.py", line 51, in build
    setup_py_data = get_setup_data(self.context.pkg, env)
  File "/usr/lib/python3/dist-packages/colcon_core/task/python/__init__.py", line 20, in get_setup_data
    return dict(pkg.metadata[key](env))
  File "/usr/lib/python3/dist-packages/colcon_ros/package_identification/ros.py", line 130, in getter
    desc.path / 'setup.py', env=env)
  File "/usr/lib/python3/dist-packages/colcon_python_setup_py/package_identification/python_setup_py.py", line 242, in get_setup_information
    setup_py, env=env)
  File "/usr/lib/python3/dist-packages/colcon_python_setup_py/package_identification/python_setup_py.py", line 286, in _get_setup_information
    return ast.literal_eval(output)
  File "/usr/lib/python3.6/ast.py", line 48, in literal_eval
    node_or_string = parse(node_or_string, mode='eval')
  File "/usr/lib/python3.6/ast.py", line 35, in parse
    return compile(source, filename, mode, PyCF_ONLY_AST)
  File "<unknown>", line 1
    Compiling object_detector/cythontest.pyx because it changed.
                            ^
SyntaxError: invalid syntax
---
Failed   <<< object_detector [0.87s, exited with code 1]
Aborted  <<< realsense2_camera [0.91s]

Summary: 4 packages finished [2.80s]
  1 package failed: object_detector
  1 package aborted: realsense2_camera
  1 package had stderr output: object_detector
invalid syntax (<unknown>, line 1)