NumPy warnings when loading FakeBackends

[nonhermitian]

Environment

• Qiskit Terra version: master
• Python version: 3.8
• Operating system: Linux

What is happening?

In looking into #7789 I discovered that master is throwing a NumPy warning when importing a fake backend

from qiskit.test.mock import FakeWashington
backend = FakeWashington()

/home/paul/mambaforge/envs/qiskit/lib/python3.8/site-packages/numpy/core/getlimits.py:499: UserWarning: The value of the smallest subnormal for <class 'numpy.float64'> type is zero.
  setattr(self, word, getattr(machar, word).flat[0])
/home/paul/mambaforge/envs/qiskit/lib/python3.8/site-packages/numpy/core/getlimits.py:89: UserWarning: The value of the smallest subnormal for <class 'numpy.float64'> type is zero.
  return self._float_to_str(self.smallest_subnormal)
/home/paul/mambaforge/envs/qiskit/lib/python3.8/site-packages/numpy/core/getlimits.py:499: UserWarning: The value of the smallest subnormal for <class 'numpy.float32'> type is zero.
  setattr(self, word, getattr(machar, word).flat[0])
/home/paul/mambaforge/envs/qiskit/lib/python3.8/site-packages/numpy/core/getlimits.py:89: UserWarning: The value of the smallest subnormal for <class 'numpy.float32'> type is zero.
  return self._float_to_str(self.smallest_subnormal)

How can we reproduce the issue?

Run the above. My NumPy is 1.22.3

What should happen?

Now UserWarning

Any suggestions?

No response

[mtreinish]

This is actually a qiskit-aer bug (it was compling with fast math by default): Qiskit/qiskit-aer#1461 It's fixed for inclusion in an upcoming bugfix release (which is in progress Qiskit/qiskit-aer#1481 ). It's triggered on the use of the fake backends because they internally import aer.

[jakelishman]

(closing as fixed upstream)