catkin build fails with rosbash errors

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I'm getting the following errors on a workspace that builds fine with catkin_make:

[ork_tests] ==> '/home/dornhege/rosws/pr2_manipulation_tests_hydro/build/ork_tests/build_env.sh /usr/bin/make cmake_check_build_system' in '/home/dornhege/rosws/pr2_manipulation_tests_hydro/build/ork_tests'
/home/dornhege/rosws/pr2_manipulation_tests_hydro/build/ork_tests/build_env.sh: 6: /opt/ros/hydro/share/rosbash/rosbash: function: not found
/home/dornhege/rosws/pr2_manipulation_tests_hydro/build/ork_tests/build_env.sh: 7: /opt/ros/hydro/share/rosbash/rosbash: [[: not found
/home/dornhege/rosws/pr2_manipulation_tests_hydro/build/ork_tests/build_env.sh: 7: /opt/ros/hydro/share/rosbash/rosbash: Linux: not found
sed: unrecognized option '--extend'
Usage: sed [OPTION]... {script-only-if-no-other-script} [input-file]...
  -n, --quiet, --silent
                 suppress automatic printing of pattern space
  -e script, --expression=script
                 add the script to the commands to be executed
  -f script-file, --file=script-file
                 add the contents of script-file to the commands to be executed
  --follow-symlinks
                 follow symlinks when processing in place
  -i[SUFFIX], --in-place[=SUFFIX]
                 edit files in place (makes backup if extension supplied)
  -l N, --line-length=N
                 specify the desired line-wrap length for the `l' command
  --posix
                 disable all GNU extensions.
  -r, --regexp-extended
                 use extended regular expressions in the script.
  -s, --separate
                 consider files as separate rather than as a single continuous
                 long stream.
  -u, --unbuffered
                 load minimal amounts of data from the input files and flush
                 the output buffers more often
      --help     display this help and exit
      --version  output version information and exit
If no -e, --expression, -f, or --file option is given, then the first
non-option argument is taken as the sed script to interpret.  All
remaining arguments are names of input files; if no input files are
specified, then the standard input is read.
GNU sed home page: <http://www.gnu.org/software/sed/>.
General help using GNU software: <http://www.gnu.org/gethelp/>.
/home/dornhege/rosws/pr2_manipulation_tests_hydro/build/ork_tests/build_env.sh: 12: /opt/ros/hydro/share/rosbash/rosbash: Syntax error: "}" unexpected

As far as I can see it the problem is that build_env.sh declares:

#!/usr/bin/env sh

Which on ubuntu defaults to dash, not bash. When later somehow rosbash is sourced, this conflicts. I believe that this should work. As far as I can tell I did not setup something uncommon. Any hints on what might cause this?