import ValidationError from asdf, drop jsonschema as a dependency (#295)

* import ValidationError from asdf, drop jsonschema as a dependency

* add changelog entry

* fix import order

* incraese minimum asdf-transform-schemas version

* add attempt to import ValidationError

first try to import ValidationError from
asdf.exceptions then fallback to importing
from the top level asdf if this fails.

* sort imports

* add changelog entry

* add comment about ValidationError import

changelog/295.bugfix.rst

@@ -0,0 +1 @@
+Import ValidationError from asdf, drop jsonschema as a dependency.

dkist/dataset/loader.py

@@ -2,11 +2,17 @@
 from pathlib import Path
 from functools import singledispatch
 
-from jsonschema.exceptions import ValidationError
 from parfive import Results
 
 import asdf
 
+try:
+    # first try to import from asdf.exceptions for asdf 2.15+
+    from asdf.exceptions import ValidationError
+except ImportError:
+    # fall back to top level asdf for older versions of asdf
+    from asdf import ValidationError
+
 
 @singledispatch
 def load_dataset(target):

setup.cfg

@@ -35,7 +35,6 @@ install_requires =
   parfive[ftp]>=1.5
   sunpy[net,asdf]>=4.0.7
   setuptools>=59
-  jsonschema>=3.2
   aiohttp>=3.6
   tqdm>=4.63
 setup_requires = setuptools_scm