The use of SHA1 found here:

digest_method = staticmethod(hashlib.sha1)

prevents applications from running in a FIPS Enabled Environment/OS. The OS will abruptly stop the application from running when it detects a non compliant Hash Algorithm is used.

Describe how to replicate the bug:
Enforce FIPS Enabled on the OS (such as RHEL9)

Unexpected Behavior Error output:

Traceback (most recent call last):
  File "/opt/abc-app/app.py", line 1, in <module>
    from xxxxxxxxxx import xxxxxxx
  File "/opt/abc-app/abc-app_ui.py", line 67, in <module>
    sess.init_app(app=app)
  File "/opt/abc-app/venv/lib/python3.11/site-packages/flask_session/__init__.py", line 50, in init_app
    app.session_interface = self._get_interface(app)
                            ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/abc-app/venv/lib/python3.11/site-packages/flask_session/__init__.py", line 79, in _get_interface
    session_interface = FileSystemSessionInterface(
                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/abc-app/venv/lib/python3.11/site-packages/flask_session/sessions.py", line 312, in __init__
    self.cache = FileSystemCache(cache_dir, threshold=threshold, mode=mode)
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/abc-app/venv/lib/python3.11/site-packages/cachelib/file.py", line 73, in __init__
    self._update_count(value=len(list(self._list_dir())))
  File "/opt/abc-app/venv/lib/python3.11/site-packages/cachelib/file.py", line 95, in _update_count
    self.set(self._fs_count_file, new_count, mgmt_element=True)
  File "/opt/abc-app/venv/lib/python3.11/site-packages/cachelib/file.py", line 244, in set
    filename = self._get_filename(key)
               ^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/abc-app/venv/lib/python3.11/site-packages/cachelib/file.py", line 201, in _get_filename
    bkey_hash = self._hash_method(bkey).hexdigest()
                ^^^^^^^^^^^^^^^^^^^^^^^
_hashlib.UnsupportedDigestmodError: [digital envelope routines] unsupported

Environment:
RHEL9 FIPS Enabled and Enforced

Python version: 3.x
Flask version: 3.0.2