diff --git a/doc/HACKING.md b/doc/HACKING.md
index a92aa34de..cf015c959 100644
--- a/doc/HACKING.md
+++ b/doc/HACKING.md
@@ -162,6 +162,12 @@ sudo apt install valgrind cppcheck shellcheck
 pip3 install -r tests/requirements.txt
 ```
 
+Re-run `configure` for the python dependencies
+
+```
+./configure
+```
+
 Tests are run with: `make check [flags]` where the pertinent flags are:
 
 ```
diff --git a/tests/requirements.txt b/tests/requirements.txt
index a20264fb9..7037dac72 100644
--- a/tests/requirements.txt
+++ b/tests/requirements.txt
@@ -1,3 +1,4 @@
+flake8==3.5.0
 pytest==3.8.1
 CherryPy==17.3.0
 Flask==1.0.2