Summary:
When you call ast.literal_eval on a string that does not contain valid Python code, it raises a SyntaxError. This causes pdb to exit instead of stopping execution at the point that the SyntaxError was raised.

To reproduce:
1. Create a Python file foo.py with these contents:

    import ast
    ast.literal_eval('')

2. Run python -m pdb foo.py
3. Type 'c' and hit enter.

Expected behavior:
pdb drops into a shell in ast.py at the point where the SyntaxError occurred.

Actual behavior:
The program exits, and a SyntaxError traceback is displayed.

System configuration:
Python 3.8.2 on Arch Linux.