/bin/sh: line 1: blurb: command not found

http://buildbot.python.org/all/#/builders/69/builds/51

Running make frameworkinstallextras
(...)
copy /Users/db3l/buildarea.dmg/bolen-dmg-3.x/build/Mac/../Tools/unittestgui/README.txt /Users/db3l/buildarea.dmg/bolen-dmg-3.x/build/dmg/_root/Library/Frameworks/Python.framework/Versions/3.7/share/doc/python3.7/examples/Tools/unittestgui/README.txt
copy /Users/db3l/buildarea.dmg/bolen-dmg-3.x/build/Mac/../Tools/unittestgui/unittestgui.py /Users/db3l/buildarea.dmg/bolen-dmg-3.x/build/dmg/_root/Library/Frameworks/Python.framework/Versions/3.7/share/doc/python3.7/examples/Tools/unittestgui/unittestgui.py
Copying required shared libraries
Fix file modes
Install python documentation
rm -rf build/* ./venv/*
make: `venv' is up to date.
/bin/sh: line 1: blurb: command not found
make: *** [build] Error 127
Traceback (most recent call last):
mkdir -p build
Building NEWS from Misc/NEWS.d with blurb
  File "/Users/db3l/buildarea.dmg/bolen-dmg-3.x/build/Mac/BuildScript/build-installer.py", line 1659, in <module>
    main()
  File "/Users/db3l/buildarea.dmg/bolen-dmg-3.x/build/Mac/BuildScript/build-installer.py", line 1621, in main
    buildPythonDocs()
  File "/Users/db3l/buildarea.dmg/bolen-dmg-3.x/build/Mac/BuildScript/build-installer.py", line 1094, in buildPythonDocs
    runCommand('make html PYTHON=venv/bin/python')
  File "/Users/db3l/buildarea.dmg/bolen-dmg-3.x/build/Mac/BuildScript/build-installer.py", line 531, in runCommand
    raise RuntimeError("command failed: %s"%(commandline,))
RuntimeError: command failed: make html PYTHON=venv/bin/python
program finished with exit code 1
elapsedTime=1288.975592