diff --git a/common/lib/capa/capa/responsetypes.py b/common/lib/capa/capa/responsetypes.py
index 65e903b576..3b17daa830 100644
--- a/common/lib/capa/capa/responsetypes.py
+++ b/common/lib/capa/capa/responsetypes.py
@@ -36,7 +36,7 @@ from datetime import datetime
 from .util import *
 from lxml import etree
 from lxml.html.soupparser import fromstring as fromstring_bs     # uses Beautiful Soup!!! FIXME?
-import xqueue_interface
+import capa.xqueue_interface
 
 log = logging.getLogger(__name__)
 
@@ -301,7 +301,7 @@ class LoncapaResponse(object):
                     # response
                     aid = self.answer_ids[-1]
                     new_cmap.set_hint_and_mode(aid, hint_text, hintmode)
-            log.debug('after hint: new_cmap = %s' % new_cmap)
+            log.debug('after hint: new_cmap = %s', new_cmap)
 
     @abc.abstractmethod
     def get_score(self, student_answers):
@@ -791,6 +791,10 @@ class OptionResponse(LoncapaResponse):
 
 
 class NumericalResponse(LoncapaResponse):
+    '''
+    This response type expects a number or formulaic expression that evaluates
+    to a number (e.g. `4+5/2^2`), and accepts with a tolerance.
+    '''
 
     response_tag = 'numericalresponse'
     hint_tag = 'numericalhint'
@@ -807,12 +811,12 @@ class NumericalResponse(LoncapaResponse):
                 '//*[@id=$id]//responseparam[@type="tolerance"]/@default',
                 id=xml.get('id'))[0]
             self.tolerance = contextualize_text(self.tolerance_xml, context)
-        except Exception:
+        except IndexError:  # xpath found an empty list, so (...)[0] is the error
             self.tolerance = '0'
         try:
             self.answer_id = xml.xpath('//*[@id=$id]//textline/@id',
                                        id=xml.get('id'))[0]
-        except Exception:
+        except IndexError:  # Same as above
             self.answer_id = None
 
     def get_score(self, student_answers):
@@ -837,7 +841,6 @@ class NumericalResponse(LoncapaResponse):
         except:
             # Use the traceback-preserving version of re-raising with a
             # different type
-            import sys
             type, value, traceback = sys.exc_info()
 
             raise StudentInputError, ("Could not interpret '%s' as a number" %