See this huge warning in the definition of PyDict_GetItem:

/* Note that, for historical reasons, PyDict_GetItem() suppresses all errors

• that may occur (originally dicts supported only string keys, and exceptions
• weren't possible). So, while the original intent was that a NULL return
• meant the key wasn't present, in reality it can mean that, or that an error
• (suppressed) occurred while computing the key's hash, or that some error
• (suppressed) occurred when comparing keys in the dict's internal probe
• sequence. A nasty example of the latter is when a Python-coded comparison
• function hits a stack-depth error, which can cause this to return NULL
• even if the key is present.
  */
  PyObject *
  PyDict_GetItem(PyObject *op, PyObject *key)
  { ... }

PyDict_GetItem() should avoided because it may hide important exceptions like KeyboardInterrupt or MemoryError.

See for example bpo-14537 for a specific error.

By the way, the PyDict_GetItem() documentation should contain a big red warning and suggest to use PyDict_GetItemWithError() instead.

Please, no more big red warnings.

Keep the docs factual and straight-forward. In the docs for PyDict_GetItem(), note that errors will get suppressed. To
get error reporting use PyDict_GetItemWithError() instead.

Sorry, I lost track of this issue, so I just close it.