Move ErrorMessage to microsoft-agents-activity to resolve circular dependency

[Copilot]

microsoft-agents-hosting-core depends on microsoft-agents-activity, but ErrorMessage was located in hosting-core and imported by activity, creating a circular dependency.

Changes

• Moved error_message.py from microsoft-agents-hosting-core to microsoft-agents-activity
• Updated imports across 6 packages (authentication-msal, copilotstudio-client, storage-blob, storage-cosmos, hosting-teams, hosting-core)
• Maintained backward compatibility via re-export in hosting-core's __init__.py

Import paths

# Canonical (recommended)
from microsoft_agents.activity.errors import ErrorMessage

# Backward compatible (still works)
from microsoft_agents.hosting.core.errors import ErrorMessage

Both imports resolve to the same class. No breaking changes.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Move ErrorMessage to microsoft-agents-activity</issue_title>
<issue_description>Move the ErrorMessage from to microsoft-agents-activity.

The current ErrorMessage file is found here:
https://github.com/microsoft/Agents-for-python/blob/10efb95e18529aaa3a1927e10add95f93683658a/libraries/microsoft-agents-hosting-core/microsoft_agents/hosting/core/errors/error_message.py

This should be moved to the location:
https://github.com/microsoft/Agents-for-python/tree/10efb95e18529aaa3a1927e10add95f93683658a/libraries/microsoft-agents-activity/microsoft_agents/activity/errors

The existing location is causing circular dependency issues across other packages.

Analyze where this is used, and update all necessary imports and tests.

</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Move ErrorMessage to microsoft-agents-activity #239

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[Copilot]

Pull Request Overview

This PR successfully resolves a circular dependency issue by moving the ErrorMessage class from microsoft-agents-hosting-core to microsoft-agents-activity, where it logically belongs as a lower-level dependency.

Key Changes:

• Relocated error_message.py from hosting-core to the activity package
• Updated imports across 6 packages to use the new canonical location
• Maintained backward compatibility by re-exporting ErrorMessage from hosting-core's __init__.py

Reviewed Changes

Copilot reviewed 14 out of 15 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
libraries/microsoft-agents-activity/microsoft_agents/activity/errors/error_message.py	New location for ErrorMessage class implementation
libraries/microsoft-agents-activity/microsoft_agents/activity/errors/__init__.py	Updated to import ErrorMessage locally and export it
libraries/microsoft-agents-activity/microsoft_agents/activity/errors/error_resources.py	Changed to use local import of ErrorMessage
libraries/microsoft-agents-hosting-core/microsoft_agents/hosting/core/errors/__init__.py	Re-exports ErrorMessage from activity package for backward compatibility
libraries/microsoft-agents-hosting-core/microsoft_agents/hosting/core/errors/error_resources.py	Updated to import ErrorMessage from activity package
libraries/microsoft-agents-authentication-msal/microsoft_agents/authentication/msal/errors/__init__.py	Updated import path to canonical location
libraries/microsoft-agents-authentication-msal/microsoft_agents/authentication/msal/errors/error_resources.py	Updated import path to canonical location
libraries/microsoft-agents-copilotstudio-client/microsoft_agents/copilotstudio/client/errors/__init__.py	Updated import path to canonical location
libraries/microsoft-agents-copilotstudio-client/microsoft_agents/copilotstudio/client/errors/error_resources.py	Updated import path to canonical location
libraries/microsoft-agents-storage-blob/microsoft_agents/storage/blob/errors/__init__.py	Updated import path to canonical location
libraries/microsoft-agents-storage-blob/microsoft_agents/storage/blob/errors/error_resources.py	Updated import path to canonical location
libraries/microsoft-agents-storage-cosmos/microsoft_agents/storage/cosmos/errors/__init__.py	Updated import path to canonical location
libraries/microsoft-agents-storage-cosmos/microsoft_agents/storage/cosmos/errors/error_resources.py	Updated import path to canonical location
libraries/microsoft-agents-hosting-teams/microsoft_agents/hosting/teams/errors/__init__.py	Updated import path to canonical location
libraries/microsoft-agents-hosting-teams/microsoft_agents/hosting/teams/errors/error_resources.py	Updated import path to canonical location

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