code: def check_dependencies():
      
      print("Checking required dependencies")
      for dep, msg in [(["git", "--version"], "Git (http://git-scm.com/)"),
                       (["wget", "--version"], "wget"),
                       (["bzip2", "-h"], "bzip2")]:
          try:
              p = subprocess.Popen(dep, stderr=subprocess.STDOUT, stdout=subprocess.PIPE)
              out, code = p.communicate()
          except OSError:
              out = "Executable not found"
              code = 127
          if code == 127:
              raise OSError("bcbio-nextgen installer requires %s\n%s" % (msg, out))
docs: Ensure required tools for installation are present.