Corrected not-so-tasty gitlab runner recipe

manuscript/generate_preview.py

@@ -0,0 +1,8 @@
+#!/usr/bin/python
+
+with open("Book.txt") as f:
+    print ('echo "Starting build of {book}.epub";'
+            "pandoc {files} " +
+            "+smart --table-of-contents --chapters -o {book}.epub;"
+            'echo "  {book}.epub created."'
+            ).format(book="Book", files=f.read().replace("\n", " "))