Update aws.md with errors (#2226)

added couple more error messages

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Author: grusev

docs/mkdocs/docs/aws.md

@@ -110,8 +110,21 @@ Use the configuration in ArcticDB:
 >>> arctic = adb.Arctic('s3://s3.REGION.amazonaws.com:BUCKET?aws_auth=sts&aws_profile=PROFILE')
 ```
 
+## Common Errors When Working with STS
+
 Due to limitations in the AWS C++ SDK, if ArcticDB fails to obtain the temporary token by assuming a role, an assertion error similar to the one below will occur:
 ```
 virtual void Aws::Auth::STSProfileCredentialsProvider::Reload(): Assertion `!profileIt->second.GetCredentials().IsEmpty()' failed.
 ```
-This is usually due to an incorrect IAM account setup or an incorrect configuration file.
+This is usually due to an incorrect IAM account setup or an incorrect configuration file.
+
+```
+arcticdb_ext.exceptions.PermissionException: E_PERMISSION Permission error: S3Error#15 AccessDenied: Access Denied for object '_arctic_cfg/cref/'
+```
+This error suggests problems with configuration file. Check Role Arn and base source profile in the file.
+
+
+```
+arcticdb_ext.exceptions.StorageException: E_S3_RETRYABLE Retry-able error: S3Error#99 : Encountered network error when sending http request for object '_arctic_cfg/cref/'
+```
+A loss of network connectivity could trigger such an error. Note, that this error will appear after several attempts to re-establish the connection