Pin versions.

slapos/software/osie-coupler/software.cfg

 # the default SlapOs profile which setup a modbus server instance usually over OSIE's coupler
 [buildout]
-#allow-picked-versions = true
+allow-picked-versions = true
 extends =
   buildout.hash.cfg
   https://lab.nexedi.com/nexedi/slapos/raw/master/stack/monitor/buildout.cfg
@@ -86,6 +86,8 @@ docutils = 0.17.1
 mistune = 0.8.4
 setuptools-scm = 6.0.1
 setuptools = 45
+bcrypt = 3.2.0
+cffi = 1.12
 
 [instance-profile]
 recipe = slapos.recipe.template:jinja2