docs: def check_infile_and_wp(curinf, curwp):
          """Check the existence of the given file and directory path.
             1. Raise Runtime exception of both not existed.
             2. If the ``curwp`` is None, the set the base folder of ``curinf`` to it.
          """
          if not os.path.exists(curinf):
              if curwp is None:
                  TauDEM.error('You must specify one of the workspace and the '
                               'full path of input file!')
              curinf = curwp + os.sep + curinf
              curinf = os.path.abspath(curinf)
              if not os.path.exists(curinf):
                  TauDEM.error('Input files parameter %s is not existed!' % curinf)
          else:
              curinf = os.path.abspath(curinf)
              if curwp is None:
                  curwp = os.path.dirname(curinf)
          return curinf, curwp