fix: complete exception handling for UpstashRedisEntityStore (#31893)

Thank you for contributing to LangChain!

- [x] **PR title**: "package: description"
- Where "package" is whichever of langchain, core, etc. is being
modified. Use "docs: ..." for purely docs changes, "infra: ..." for CI
changes.
  - Example: "core: add foobar LLM"


- [x] **PR message**: ***Delete this entire checklist*** and replace
with
    - **Description:** a description of the change
    - **Issue:** the issue # it fixes, if applicable
    - **Dependencies:** any dependencies required for this change
- **Twitter handle:** if your PR gets announced, and you'd like a
mention, we'll gladly shout you out!


- [x] **Add tests and docs**: If you're adding a new integration, please
include
1. a test for the integration, preferably unit tests that do not rely on
network access,
2. an example notebook showing its use. It lives in
`docs/docs/integrations` directory.


- [x] **Lint and test**: Run `make format`, `make lint` and `make test`
from the root of the package(s) you've modified. See contribution
guidelines for more: https://python.langchain.com/docs/contributing/

Additional guidelines:
- Make sure optional dependencies are imported within a function.
- Please do not add dependencies to pyproject.toml files (even optional
ones) unless they are required for unit tests.
- Most PRs should not touch more than one package.
- Changes should be backwards compatible.

If no one reviews your PR within a few days, please @-mention one of
baskaryan, eyurtsev, ccurme, vbarda, hwchase17.

libs/langchain/langchain/memory/entity.py

@@ -126,8 +126,10 @@ class UpstashRedisEntityStore(BaseEntityStore):
 
         try:
             self.redis_client = Redis(url=url, token=token)
-        except Exception:
-            logger.error("Upstash Redis instance could not be initiated.")
+        except Exception as exc:
+            error_msg = "Upstash Redis instance could not be initiated"
+            logger.error(error_msg)
+            raise RuntimeError(error_msg) from exc
 
         self.session_id = session_id
         self.key_prefix = key_prefix