Switching CRDS bestrefs call from subprocess shell call to the crds.a…

…ssign_bestrefs() function based on Bandit security scan results.

notebooks/STIS/drizpac_notebook/STIS_DrizzlePac_Tutorial.ipynb

@@ -98,6 +98,7 @@
     "from drizzlepac import tweakreg\n",
     "from drizzlepac import astrodrizzle as ad\n",
     "from astroquery.mast import Observations\n",
+    "from crds import assign_bestrefs\n",
     "\n",
     "# Custom package, copy_files.py should be in the same directory\n",
     "import copy_files as cf\n",
@@ -416,7 +417,7 @@
    "source": [
     "## Download Reference Files\n",
     "\n",
-    "The reference files for the STIS images are then updated in the image headers and downloaded (~250 MB). While the `crds.bestrefs` tool is also accessible inside of Python, it was designed with a command line interface in mind, therefore it is easiest to use it this way."
+    "The reference files for the STIS images are then updated in the image headers and downloaded (~250 MB). [The `crds.bestrefs` tool](https://hst-crds.stsci.edu/docs/cmdline_bestrefs/) is also accessible from the command line interface."
    ]
   },
   {
@@ -429,8 +430,9 @@
     "# Find and update the headers with the best reference files and download them\n",
     "def download_ref_files(image_list):\n",
     "    print('Downloading reference files for:\\n{}\\n'.format(image_list))\n",
-    "    images = ' '.join(image_list)\n",
-    "    subprocess.check_output('crds bestrefs --files {} --sync-references=1 --update-bestrefs'.format(images), shell=True, stderr=subprocess.DEVNULL)\n",
+    "    errors = assign_bestrefs(image_list, sync_references=True, verbosity=-1)\n",
+    "    if len(errors) > 0:\n",
+    "        raise ValueError('Unexpected error(s) running CRDS assign_bestrefs script.')\n",
     "\n",
     "\n",
     "# Check in the Notebook directory\n",