Fixes want to read status slug

bookwyrm/templates/snippets/reading_modals/want_to_read_modal.html

@@ -10,6 +10,6 @@ Want to Read "<em>{{ book_title }}</em>"
 
 {% block modal-form-open %}
 <form name="shelve" action="{% url 'reading-status' 'want' book.id %}" method="post">
-<input type="hidden" name="reading_status" value="toRead">
+<input type="hidden" name="reading_status" value="to-read">
 {% csrf_token %}
 {% endblock %}

bookwyrm/views/reading.py

@@ -83,7 +83,7 @@ class ReadingStatus(View):
                     form.save()
                 else:
                     # uh oh
-                    raise Exception("Invalid form")
+                    raise Exception(form.errors)
             else:
                 privacy = request.POST.get("privacy")
                 handle_reading_status(request.user, desired_shelf, book, privacy)