message: drakefile: make sure //install checks for --prefix being defined
diff: @@ -1400,9 +1400,6 @@ using python : %(python_version)s : %(python_prefix)s/%(python_bin)s : %(python_
  ## Install ##
  ## ------- ##
  - if prefix is not False:
  - rule_install = drake.Rule('install')
  -
  config += cryptography.config
  config += elle.config
  config += protocol.config
  @@ -1436,6 +1433,7 @@ using python : %(python_version)s : %(python_prefix)s/%(python_bin)s : %(python_
  rule_check = drake.Rule('check')
  recurse(rule_check, 'rule_check')
  + if prefix:
  rule_install = drake.Rule('install')
  recurse(rule_install, 'rule_install')
  