Remove runtime dependency on pytest

The import here

https://github.com/astropy/astropy/blob/81804cf0d30c37c117081b4826d938ba84bfdada/astropy/io/misc/asdf/tags/coordinates/skycoord.py#L9

Gives a runtime dependency of astropy’s asdf extension on pytest, which is not desired.

To reproduce, and a traceback:

In [1]: import asdf

In [2]: from astropy.coordinates import SkyCoord

In [3]: coord = SkyCoord(ra=15, dec=12, unit='deg')

In [4]: tree = {'coord': coord}

In [5]: af = asdf.AsdfFile(tree=tree)
---------------------------------------------------------------------------
ModuleNotFoundError                       Traceback (most recent call last)
<ipython-input-5-97f03a40ab48> in <module>
----> 1 af = asdf.AsdfFile(tree=tree)

~/miniconda3/envs/test/lib/python3.7/site-packages/asdf/asdf.py in __init__(self, tree, uri, extensions, version, ignore_version_mismatch, ignore_unrecognized_tag, ignore_implicit_conversion, copy_arrays, lazy_load, custom_schema, _readonly)
    120         self._extension_metadata = {}
    121 
--> 122         self._process_extensions(extensions)
    123         self._ignore_version_mismatch = ignore_version_mismatch
    124         self._ignore_unrecognized_tag = ignore_unrecognized_tag

~/miniconda3/envs/test/lib/python3.7/site-packages/asdf/asdf.py in _process_extensions(self, extensions)
    204     def _process_extensions(self, extensions):
    205         if extensions is None or extensions == []:
--> 206             self._extensions = default_extensions.extension_list
    207             self._extension_metadata = default_extensions.package_metadata
    208             return

~/miniconda3/envs/test/lib/python3.7/site-packages/asdf/extension.py in extension_list(self)
    231     def extension_list(self):
    232         if self._extension_list is None:
--> 233             self._extension_list = AsdfExtensionList(self.extensions)
    234 
    235         return self._extension_list

~/miniconda3/envs/test/lib/python3.7/site-packages/asdf/extension.py in extensions(self)
    224                 self._extensions.append(BuiltinExtension())
    225 
--> 226             self._load_installed_extensions()
    227 
    228         return self._extensions

~/miniconda3/envs/test/lib/python3.7/site-packages/asdf/extension.py in _load_installed_extensions(self, group)
    195             with warnings.catch_warnings(record=True) as w:
    196                 warnings.simplefilter('always', category=AsdfDeprecationWarning)
--> 197                 ext = entry_point.load()
    198             if not issubclass(ext, AsdfExtension):
    199                 warnings.warn("Found entry point {}, from {} but it is not a "

~/miniconda3/envs/test/lib/python3.7/site-packages/pkg_resources/__init__.py in load(self, require, *args, **kwargs)
   2432         if require:
   2433             self.require(*args, **kwargs)
-> 2434         return self.resolve()
   2435 
   2436     def resolve(self):

~/miniconda3/envs/test/lib/python3.7/site-packages/pkg_resources/__init__.py in resolve(self)
   2438         Resolve the entry point from its module and attrs.
   2439         """
-> 2440         module = __import__(self.module_name, fromlist=['__name__'], level=0)
   2441         try:
   2442             return functools.reduce(getattr, self.attrs, module)

~/miniconda3/envs/test/lib/python3.7/site-packages/astropy/io/misc/asdf/extension.py in <module>
     15 from .tags.coordinates.frames import *
     16 from .tags.coordinates.earthlocation import *
---> 17 from .tags.coordinates.skycoord import *
     18 from .tags.coordinates.representation import *
     19 from .tags.fits.fits import *

~/miniconda3/envs/test/lib/python3.7/site-packages/astropy/io/misc/asdf/tags/coordinates/skycoord.py in <module>
      7 
      8 from astropy.coordinates import SkyCoord
----> 9 from astropy.table.tests.test_operations import skycoord_equal
     10 
     11 from ...types import AstropyType

~/miniconda3/envs/test/lib/python3.7/site-packages/astropy/table/tests/test_operations.py in <module>
      4 from collections import OrderedDict
      5 
----> 6 import pytest
      7 import numpy as np
      8 

ModuleNotFoundError: No module named 'pytest'

[astrojuanlu]

oh, wow, that should never be imported from there…

Speaking of which, I learned about the existence of this package recently, just FYI https://pypi.org/project/import-linter/

[dhomeier]

$ grep -r "allclose_jd = " astropy
astropy/io/misc/asdf/tags/time/timedelta.py:allclose_jd = functools.partial(np.allclose, rtol=2. ** -52, atol=0)

I don’t find this in the version on master. Declaring them locally would of course at least allow you to get rid of the import.