fixup! DemoStorage: Add support for deleteObject (IExternalGC)

Make flake8 happy

src/ZODB/DemoStorage.py:388:80: E501 line too long (89 > 79 characters)
src/ZODB/DemoStorage.py:391:80: E501 line too long (87 > 79 characters)
src/ZODB/DemoStorage.py:393:80: E501 line too long (83 > 79 characters)
src/ZODB/DemoStorage.py:395:80: E501 line too long (87 > 79 characters)
src/ZODB/DemoStorage.py:397:80: E501 line too long (100 > 79 characters)
src/ZODB/DemoStorage.py:398:80: E501 line too long (86 > 79 characters)
src/ZODB/DemoStorage.py:408:5: E303 too many blank lines (2)
src/ZODB/tests/testDemoStorage.py:397:9: F401 'ZODB.FileStorage.FileStorage' imported but unused
src/ZODB/tests/testDemoStorage.py:399:80: E501 line too long (101 > 79 characters)

src/ZODB/DemoStorage.py

@@ -385,17 +385,22 @@ class DemoStorage(ConflictResolvingStorage):
         # call changes.deleteObject(oldserial=z64)
 
         changesHead = self.changes.lastTransaction()
-        _, serial = ZODB.utils.loadBeforeEx(self.changes, oid, p64(u64(changesHead) + 1))
+        _, serial = ZODB.utils.loadBeforeEx(self.changes, oid,
+                                            p64(u64(changesHead) + 1))
         if serial != ZODB.utils.z64:
             # object has data or deletion record in changes
-            raise ZODB.POSException.ConflictError(oid=oid, serials=(serial, oldserial))
+            raise ZODB.POSException.ConflictError(oid=oid,
+                                                  serials=(serial, oldserial))
 
-        _, serial = ZODB.utils.loadBeforeEx(self.base, oid, p64(u64(baseHead) + 1))
+        _, serial = ZODB.utils.loadBeforeEx(self.base, oid,
+                                            p64(u64(baseHead) + 1))
         if serial != oldserial:
-            raise ZODB.POSException.ConflictError(oid=oid, serials=(serial, oldserial))
+            raise ZODB.POSException.ConflictError(oid=oid,
+                                                  serials=(serial, oldserial))
 
-        # object has no data/deletion record in changes and its latest revision in base == oldserial
-        # -> changes.deleteObject(oldserial=z64) + correct oldserial back on conflict.
+        # object has no data/deletion record in changes and its latest revision
+        # in base == oldserial. -> changes.deleteObject(oldserial=z64) +
+        # correct oldserial back on conflict.
         try:
             self.changes.deleteObject(oid, ZODB.utils.z64, transaction)
         except ZODB.POSException.ConflictError as e:
@@ -404,7 +409,6 @@ class DemoStorage(ConflictResolvingStorage):
             e.serials = (e.serials[0], oldserial)
             raise
 
-
     def storeBlob(self, oid, oldserial, data, blobfilename, version,
                   transaction):
         assert version == '', "versions aren't supported"

src/ZODB/tests/testDemoStorage.py

@@ -394,9 +394,10 @@ def test_suite():
     suite.addTest(unittest.makeSuite(DemoStorageTests2, 'check'))
 
     def demo_for_gctest():
-        from ZODB.FileStorage import FileStorage
         base = ZODB.FileStorage.FileStorage('data.fs', blob_dir="data_blobs")
-        changes = ZODB.FileStorage.FileStorage('changes.fs', blob_dir="changes_blobs", pack_gc=False)
+        changes = ZODB.FileStorage.FileStorage('changes.fs',
+                                               blob_dir="changes_blobs",
+                                               pack_gc=False)
         return ZODB.DemoStorage.DemoStorage(base=base, changes=changes)
     suite.addTest(PackableStorage.IExternalGC_suite(demo_for_gctest))