Finish up flake8 conversion.

Change-Id: I5034f19d5f9b20ad2b4569455273c730b1efec08
diff --git a/tempest/tests/boto/utils/wait.py b/tempest/tests/boto/utils/wait.py
index c2d4ea3..6cd17a9 100644
--- a/tempest/tests/boto/utils/wait.py
+++ b/tempest/tests/boto/utils/wait.py
@@ -19,7 +19,7 @@
 import re
 import time
 
-from boto.exception import BotoServerError
+import boto.exception
 from testtools import TestCase
 
 import tempest.config
@@ -87,7 +87,7 @@
     """Stops waiting on success."""
     start_time = time.time()
     if exc_matcher is not None:
-        exc_class = BotoServerError
+        exc_class = boto.exception.BotoServerError
 
     if exc_class is None:
         exc_class = BaseException