hashlib.md5 doesn't work when FIPS is enabled

[henry2004y]

Similar to this issue, while importing yt 4.4.0, I encountered the following error on Pleiades, a cluster managed by NASA:

Python 3.12.10 (main, Apr 22 2025, 18:32:49) [GCC 10.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import yt
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home1/hzhou4/swbuild/Python-3.12.10/lib/python3.12/site-packages/yt/__init__.py", line 12, in <module>
    import yt.units as units
  File "/home1/hzhou4/swbuild/Python-3.12.10/lib/python3.12/site-packages/yt/units/__init__.py", line 1, in <module>
    from unyt.array import (
  File "/home1/hzhou4/swbuild/Python-3.12.10/lib/python3.12/site-packages/unyt/__init__.py", line 38, in <module>
    from unyt import physical_constants, unit_symbols
  File "/home1/hzhou4/swbuild/Python-3.12.10/lib/python3.12/site-packages/unyt/physical_constants.py", line 22, in <module>
    _add_constants(globals(), registry=_default_unit_registry)
  File "/home1/hzhou4/swbuild/Python-3.12.10/lib/python3.12/site-packages/unyt/unit_systems.py", line 91, in add_constants
    namespace[name] = quan.in_base(unit_system=registry.unit_system)
                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home1/hzhou4/swbuild/Python-3.12.10/lib/python3.12/site-packages/unyt/array.py", line 1044, in in_base
    conv_data = _check_em_conversion(
                ^^^^^^^^^^^^^^^^^^^^^
  File "/home1/hzhou4/swbuild/Python-3.12.10/lib/python3.12/site-packages/unyt/unit_object.py", line 312, in __hash__
    return int(self.registry.unit_system_id, 16) ^ hash(self.expr)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home1/hzhou4/swbuild/Python-3.12.10/lib/python3.12/site-packages/unyt/unit_registry.py", line 96, in unit_system_id
    m = md5()
        ^^^^^
ValueError: [digital envelope routines: EVP_DigestInit_ex] disabled for FIPS

The following workaround seems to fix the problem:

m = md5(usedforsecurity=False)

However, in yt it seems there are more places calling md5().

[neutrinoceros]

The following workaround seems to fix the problem

Indeed, that's the correct fix. I'll happily accept a PR with this change.

However, in yt it seems there are more places calling md5().

Indeed. Can you please open a report (or even a PR) there too ? unyt and yt are maintained as separate projects.

[neutrinoceros]

(sorry for my delayed answer)

[henry2004y]

I will open a issue for yt! I tried to change this only in unyt. Although I had no issue import the yt package, I encountered other errors when trying to load the data.