message: Document the allowed chars in the session name
diff: # Copyright 2016-2020, Pulumi Corporation. All rights reserved.
  import pulumi_aws as aws
  -from pulumi_aws.config.vars import region
  from pulumi import Config, ResourceOptions, export
  config = Config()
  @@ -12,6 +11,9 @@ provider = aws.Provider(
  'privileged',
  assume_role={
  'role_arn': role_to_assume_arn,
  + # session name can contain only the following special characters =,.@-
  + # if any other special character is used, an error stating that the role
  + # cannot be assumed will be returned
  'session_name': 'PulumiSession',
  'externalId': 'PulumiApplication',
  },
  