docs: def check_imagemagick_supported_format(fmt):
      """
      Return ``True`` if `convert` can be run and reports supporting image format `fmt`.
      """
      try:
          convert_output = check_output(['convert', '--version'])
      # `subprocess` raises `OSError` if the executable is not found
      except (CalledProcessError, OSError) as err:
          logger.error(
              "Cannot run ImageMgick's `convert` program."
              " On Debian/Ubuntu, use `sudo apt-get install imagemagick`"
              " to install it.")
          return False
      # example `convert --version` output::
      #
      #     $ convert --version
      #     Version: ImageMagick 6.9.7-4 Q16 x86_64 20170114 http://www.imagemagick.org
      #     Copyright: (c) 1999-2017 ImageMagick Studio LLC
      #     License: http://www.imagemagick.org/script/license.php
      #     Features: Cipher DPC Modules OpenMP
      #     Delegates (built-in): bzlib djvu fftw fontconfig freetype jbig jng jpeg lcms lqr ltdl lzma openexr pangocairo png tiff wmf x xml zlib
      #
      # the following loop will make it such that::
      #
      #     supported = ['bzlib', 'djvu', ...]
      #
      supported = []
      for line in convert_output.split('\n'):
          line = line.lower()
          if line.startswith('delegates'):
              supported += line.split(':', 1)[1].split()
      # allow fmt to be ``png``, ``JPEG``, ``.TIF`` etc.
      fmt = fmt.lower()
      if not fmt.startswith('.'):
          fmt = '.' + fmt
      try:
          delegate = SUPPORTED_IMAGE_FORMATS[fmt]
      except KeyError:
          logger.error("Image format `%s` not supported by `tm_client`.")
          return False
      if delegate in supported:
          return True
      else:
          logger.error("Image format `%s` not in ImageMagick's `convert` delegates.")
          return False