Uninterruptible Execution Upon Error in Google Colab

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Describe the bug

If any error occurs when using CUDA-Q in Google Colab, the execution often becomes uninterruptible, and would require restarting the entire Colab session. This makes REPL trial-and-error editing difficult on Colab.

This issue doesn't seem to occur when running a python script on a local machine, or using a self-hosted jupyter lab.

Potentially related: https://github.com/NVIDIA/cuda-quantum/issues/244, https://github.com/NVIDIA/cuda-quantum/issues/1764

Thanks @Squirtle007 and @y-h-Lin for helping confirm this issue.

Steps to reproduce the bug

• Open a New Notebook on Colab
• Create and Execute Cell 1:

  !pip install cudaq
  

• Create and Execute Cell 2:

  import cudaq
  print(A)
  

• Observe the uninterruptible execution.
  
  

Full Error Message:

ERROR:root:Internal Python error in the inspect module.
Below is the traceback from this internal error.

ERROR:root:Internal Python error in the inspect module.
Below is the traceback from this internal error.

ERROR:root:Internal Python error in the inspect module.
Below is the traceback from this internal error.

NameError: name 'A' is not defined

During handling of the above exception, another exception occurred:

AttributeError: 'NameError' object has no attribute '_render_traceback_'

During handling of the above exception, another exception occurred:

AssertionError
NameError: name 'A' is not defined

During handling of the above exception, another exception occurred:

AttributeError: 'NameError' object has no attribute '_render_traceback_'

During handling of the above exception, another exception occurred:

TypeError: object of type 'NoneType' has no len()

During handling of the above exception, another exception occurred:

AttributeError: 'TypeError' object has no attribute '_render_traceback_'

During handling of the above exception, another exception occurred:

AssertionError
NameError: name 'A' is not defined

During handling of the above exception, another exception occurred:

AttributeError: 'NameError' object has no attribute '_render_traceback_'

During handling of the above exception, another exception occurred:

TypeError: object of type 'NoneType' has no len()

During handling of the above exception, another exception occurred:

AttributeError: 'TypeError' object has no attribute '_render_traceback_'

During handling of the above exception, another exception occurred:

TypeError: object of type 'NoneType' has no len()

During handling of the above exception, another exception occurred:

AttributeError: 'TypeError' object has no attribute '_render_traceback_'

During handling of the above exception, another exception occurred:

AssertionError

Expected behavior

When an error occurred, the execution should be interruptible by clicking the Stop button, and should not require a session restart.

Is this a regression? If it is, put the last known working version (or commit) here.

Not a regression

Environment

• CUDA-Q version: 0.9.1
  (!pip install cudaq on Google Colab)
• Python version: Python 3.10.12
  (!python --version on Google Colab)
• C++ compiler: gcc (Ubuntu 11.4.0-1ubuntu1~22.04) 11.4.0
  (!gcc --version on Google Colab)
• Operating system: Ubuntu 22.04.3 LTS
  (!lsb_release -a on Google Colab)

Suggestions

No response

Start by reproducing the failure in a fresh Google Colab notebook with CUDA-Q 0.9.1, using the two cells and traceback shown in the issue; compare it with a local Python script or self-hosted JupyterLab. Trace the error-handling path around the inspect and render_traceback failures, and consider related issues 244 and 1764. Done means a cell error remains interruptible through Colab’s Stop button without restarting the session.