Handle exceptions when constructing DefaultAzureCredential (#8294)

Author: chlowell

sdk/identity/azure-identity/HISTORY.md

@@ -1,6 +1,8 @@
 # Release History
 
 ### 1.1.0b1 Unreleased
+- Constructing `DefaultAzureCredential` no longer raises `ImportError` on Python
+3.8 on Windows ([8294](https://github.com/Azure/azure-sdk-for-python/pull/8294))
 
 
 ### 2019-11-05 1.0.1

sdk/identity/azure-identity/azure/identity/_credentials/default.py

@@ -2,6 +2,7 @@
 # Copyright (c) Microsoft Corporation.
 # Licensed under the MIT License.
 # ------------------------------------
+import logging
 import os
 
 from azure.core.exceptions import ClientAuthenticationError
@@ -12,6 +13,8 @@
 from .managed_identity import ManagedIdentityCredential
 from .user import SharedTokenCacheCredential
 
+_LOGGER = logging.getLogger(__name__)
+
 
 class DefaultAzureCredential(ChainedTokenCredential):
     """A default credential capable of handling most Azure SDK authentication scenarios.
@@ -37,11 +40,14 @@ def __init__(self, **kwargs):
 
         # SharedTokenCacheCredential is part of the default only on supported platforms.
         if SharedTokenCacheCredential.supported():
-            credentials.append(
-                SharedTokenCacheCredential(
-                    username=os.environ.get(EnvironmentVariables.AZURE_USERNAME), authority=authority, **kwargs
-                )
-            )
+            try:
+                # username is only required to disambiguate, when the cache contains tokens for multiple identities
+                username = os.environ.get(EnvironmentVariables.AZURE_USERNAME)
+                shared_cache = SharedTokenCacheCredential(username=username, authority=authority, **kwargs)
+                credentials.append(shared_cache)
+            except Exception as ex:  # pylint:disable=broad-except
+                # transitive dependency pywin32 doesn't support 3.8 (https://github.com/mhammond/pywin32/issues/1431)
+                _LOGGER.info("Shared token cache is unavailable: '%s'", ex)
 
         super(DefaultAzureCredential, self).__init__(*credentials)
 

sdk/identity/azure-identity/azure/identity/aio/_credentials/default.py

@@ -2,6 +2,7 @@
 # Copyright (c) Microsoft Corporation.
 # Licensed under the MIT License.
 # ------------------------------------
+import logging
 import os
 
 from ..._constants import EnvironmentVariables
@@ -10,6 +11,8 @@
 from .managed_identity import ManagedIdentityCredential
 from .user import SharedTokenCacheCredential
 
+_LOGGER = logging.getLogger(__name__)
+
 
 class DefaultAzureCredential(ChainedTokenCredential):
     """A default credential capable of handling most Azure SDK authentication scenarios.
@@ -35,10 +38,13 @@ def __init__(self, **kwargs):
 
         # SharedTokenCacheCredential is part of the default only on supported platforms.
         if SharedTokenCacheCredential.supported():
-            credentials.append(
-                SharedTokenCacheCredential(
-                    username=os.environ.get(EnvironmentVariables.AZURE_USERNAME), authority=authority, **kwargs
-                )
-            )
+            try:
+                # username is only required to disambiguate, when the cache contains tokens for multiple identities
+                username = os.environ.get(EnvironmentVariables.AZURE_USERNAME)
+                shared_cache = SharedTokenCacheCredential(username=username, authority=authority, **kwargs)
+                credentials.append(shared_cache)
+            except Exception as ex:  # pylint:disable=broad-except
+                # transitive dependency pywin32 doesn't support 3.8 (https://github.com/mhammond/pywin32/issues/1431)
+                _LOGGER.info("Shared token cache is unavailable: '%s'", ex)
 
         super().__init__(*credentials)