Always use Pydantic v1 API, test using v1 and v2

.github/workflows/CI.yaml

@@ -25,7 +25,7 @@ jobs:
       matrix:
         os: [ubuntu-latest, macOS-latest]
         python-version: ["3.10", "3.11"]
-        pydantic-version: ["1"]
+        pydantic-version: ["1", "2"]
         openeye: [true, false]
         integration: [true]
 

openff/bespokefit/_pydantic.py

@@ -1,41 +1,22 @@
 """A set of common utilities and types useful for building pydantic models."""
 
 import numpy
-
-try:
-    from pydantic.v1 import BaseModel as PydanticBaseModel
-    from pydantic.v1 import (
-        BaseSettings,
-        Extra,
-        Field,
-        PositiveFloat,
-        PositiveInt,
-        ValidationError,
-        conint,
-        conlist,
-        parse_file_as,
-        parse_obj_as,
-        parse_raw_as,
-        validator,
-    )
-    from pydantic.v1.generics import GenericModel
-except ImportError:
-    from pydantic import BaseModel as PydanticBaseModel
-    from pydantic import (  # noqa
-        BaseSettings,
-        Extra,
-        Field,
-        PositiveFloat,
-        PositiveInt,
-        ValidationError,
-        conint,
-        conlist,
-        parse_file_as,
-        parse_obj_as,
-        parse_raw_as,
-        validator,
-    )
-    from pydantic.generics import GenericModel  # noqa
+from pydantic.v1 import BaseModel as PydanticBaseModel
+from pydantic.v1 import (
+    BaseSettings,
+    Extra,
+    Field,
+    PositiveFloat,
+    PositiveInt,
+    ValidationError,
+    conint,
+    conlist,
+    parse_file_as,
+    parse_obj_as,
+    parse_raw_as,
+    validator,
+)
+from pydantic.v1.generics import GenericModel
 
 
 class BaseModel(PydanticBaseModel):