old_contents: import pbt
  import sys
  import os
  
  
  @pbt.command(name="install")
  def install(ctx, args, project):
      """
      Works as a wrapper for pip, with some sugar
      """
  
      try:
          import pip
      except ImportError:
          print("You need pip in order to use install, please see "
                "http://www.pip-installer.org/en/latest/installing.html")
          sys.exit(0)
  
      if args:
          pip.main(["install"] + args)
      else:
          # try to fetch the requirements.txt of the project
          if os.path.exists("requirements.txt"):
              pip.main(["install", "-r", "requirements.txt"])
          else:
              print("there is not requirements.txt file in the current folder")
  
new_contents: import pbt
  import sys
  import os
  
  
  @pbt.command(name="install")
  def install(ctx, args, project):
      """
      Works as a wrapper for pip, with some sugar
      """
  
      try:
          import pip
      except ImportError:
          print("You need pip in order to use install, please see "
                "http://www.pip-installer.org/en/latest/installing.html")
          sys.exit(0)
  
      if args:
          pip.main(["install"] + args)
      else:
          deps_spec = ["".join(dep) for dep in project.dependencies]
          # make it configurable?
          target_path = project.join_path("deps")
          ctx.ensure_dir_exists(target_path)
  
          args = ["install", "-t", target_path] + deps_spec
          pip.main(args)
  
subject: install from project.pbt dependencies into deps