diff --git a/doc/misc.rst b/doc/misc.rst
index dfa2557b0f5e2c3c3e83bc1011169ef23c5a1025..99fc8ab0019ff9642540eef3276e0b01eb6007ea 100644
--- a/doc/misc.rst
+++ b/doc/misc.rst
@@ -21,7 +21,8 @@ Enter the relate directory::
 
     cd relate
 
-Install the dependencies::
+Edit :file:`requirements.txt` to choose a version of `dnspython`, then install
+the dependencies::
 
     pip install -r requirements.txt
 
diff --git a/run-tests-for-ci.sh b/run-tests-for-ci.sh
index fb16dcd6c43c053d98539d7ac306359a6684bc62..ab6ed9dedfd6b45d0e7bb383d180fade655f8d3f 100644
--- a/run-tests-for-ci.sh
+++ b/run-tests-for-ci.sh
@@ -1,5 +1,7 @@
 #! /bin/bash
 
+set -e
+
 echo "-----------------------------------------------"
 echo "Current directory: $(pwd)"
 echo "Python executable: ${PY_EXE}"
@@ -54,7 +56,15 @@ export PATH=`pwd`/.env/local/bin:$PATH
 
 PIP="${PY_EXE} $(which pip)"
 
-$PIP install -r requirements.txt
+grep -v dnspython requirements.txt > req.txt
+if [[ "$PY_EXE" = "python2*" ]]; then
+  $PIP install dnspython
+else
+  $PIP install dnspython3
+fi
+
+$PIP install -r req.txt
+
 cp local_settings.py.example local_settings.py
 
 cd test