improve bad epub error handling

frontend/views.py

@@ -135,6 +135,7 @@ from regluit.payment.parameters import (
 
 from regluit.utils.localdatetime import now, date_today
 from regluit.booxtream.exceptions import BooXtreamError
+from regluit.pyepub import InvalidEpub
 from regluit.libraryauth.views import Authenticator
 from regluit.libraryauth.models import Library
 
@@ -436,7 +437,7 @@ def edition_uploads(request, edition_id):
             try:
                 test_acq.get_watermarked()
                 context['watermarked']= test_acq.watermarked
-            except (BooXtreamError, ET.ParseError) as e:
+            except (BooXtreamError, ET.ParseError, InvalidEpub) as e:
                 context['upload_error']= e
                 form.instance.delete()
 

pyepub/__init__.py

@@ -137,8 +137,7 @@ class EPUB(zipfile.ZipFile):
             self.id = self.opf.find('.//{0}identifier[@id="{1}"]'.format(NAMESPACE["dc"],
                                                                          self.opf.get("unique-identifier"))).text
         except AttributeError:
-            raise InvalidEpub  # Cannot process an EPUB without unique-identifier
-                               # attribute of the package element
+            raise InvalidEpub("Cannot process an EPUB without unique-identifier attribute of the package element")
         # Get and parse the TOC
         toc_id = self.opf[2].get("toc")
         expr = ".//{0}item[@id='{1:s}']".format(NAMESPACE["opf"], toc_id)