2011-10-12 19:07:42+0200 [-] [txdav.common.datastore.util.UpgradeDatabaseSchemaService#warn] Beginning database schema check.
2011-10-12 19:07:42+0200 [-] [txdav.common.datastore.util.UpgradeDatabaseSchemaService#warn] Required schema version: 6.
2011-10-12 19:07:42+0200 [-] [txdav.common.datastore.util.UpgradeDatabaseSchemaService#warn] Actual schema version: 4.
2011-10-12 19:07:42+0200 [-] [txdav.common.datastore.util.UpgradeDatabaseSchemaService#warn] Starting schema upgrade from version 4 to 6.
2011-10-12 19:07:42+0200 [-] [txdav.common.datastore.util.UpgradeDatabaseSchemaService#warn] Applying schema upgrade: upgrade_from_4_to_5.sql
2011-10-12 19:07:43+0200 [-] Unhandled error in Deferred:
2011-10-12 19:07:43+0200 [-] Unhandled Error
	Traceback (most recent call last):
	  File "/usr/lib64/python2.7/site-packages/twisted/internet/defer.py", line 388, in errback
	    self._startRunCallbacks(fail)
	  File "/usr/lib64/python2.7/site-packages/twisted/internet/defer.py", line 455, in _startRunCallbacks
	    self._runCallbacks()
	  File "/usr/lib64/python2.7/site-packages/twisted/internet/defer.py", line 542, in _runCallbacks
	    current.result = callback(current.result, *args, **kw)
	  File "/usr/lib64/python2.7/site-packages/twisted/internet/defer.py", line 1076, in gotResult
	    _inlineCallbacks(r, g, deferred)
	--- <exception caught here> ---
	  File "/usr/lib64/python2.7/site-packages/twisted/internet/defer.py", line 1018, in _inlineCallbacks
	    result = result.throwExceptionIntoGenerator(g)
	  File "/usr/lib64/python2.7/site-packages/twisted/python/failure.py", line 350, in throwExceptionIntoGenerator
	    return g.throw(self.type, self.value, self.tb)
	  File "/usr/lib64/python2.7/site-packages/txdav/common/datastore/util.py", line 302, in doUpgrade
	    yield self.upgradeVersion(actual_version, required_version, dialect)
	  File "/usr/lib64/python2.7/site-packages/twisted/internet/defer.py", line 1018, in _inlineCallbacks
	    result = result.throwExceptionIntoGenerator(g)
	  File "/usr/lib64/python2.7/site-packages/twisted/python/failure.py", line 350, in throwExceptionIntoGenerator
	    return g.throw(self.type, self.value, self.tb)
	  File "/usr/lib64/python2.7/site-packages/txdav/common/datastore/util.py", line 332, in upgradeVersion
	    yield self.applyUpgrade(sqlTxn, fp)
	  File "/usr/lib64/python2.7/site-packages/twisted/internet/defer.py", line 1018, in _inlineCallbacks
	    result = result.throwExceptionIntoGenerator(g)
	  File "/usr/lib64/python2.7/site-packages/twisted/python/failure.py", line 350, in throwExceptionIntoGenerator
	    return g.throw(self.type, self.value, self.tb)
	  File "/usr/lib64/python2.7/site-packages/txdav/common/datastore/util.py", line 394, in applyUpgrade
	    yield sqlTxn.execSQLBlock(sql)
	  File "/usr/lib64/python2.7/site-packages/twisted/internet/defer.py", line 1018, in _inlineCallbacks
	    result = result.throwExceptionIntoGenerator(g)
	  File "/usr/lib64/python2.7/site-packages/twisted/python/failure.py", line 350, in throwExceptionIntoGenerator
	    return g.throw(self.type, self.value, self.tb)
	  File "/usr/lib64/python2.7/site-packages/txdav/common/datastore/sql.py", line 532, in execSQLBlock
	    yield self.execSQL(stmt)
	  File "/usr/lib64/python2.7/site-packages/twisted/internet/defer.py", line 1018, in _inlineCallbacks
	    result = result.throwExceptionIntoGenerator(g)
	  File "/usr/lib64/python2.7/site-packages/twisted/python/failure.py", line 350, in throwExceptionIntoGenerator
	    return g.throw(self.type, self.value, self.tb)
	  File "/usr/lib64/python2.7/site-packages/txdav/common/datastore/sql.py", line 511, in execSQL
	    results = (yield self._sqlTxn.execSQL(*a, **kw))
	  File "/usr/lib64/python2.7/site-packages/twext/internet/threadutils.py", line 64, in _oneWorkUnit
	    result = instruction()
	  File "/usr/lib64/python2.7/site-packages/twext/enterprise/adbapi2.py", line 293, in <lambda>
	    lambda : self._reallyExecSQL(*args, **kw)
	  File "/usr/lib64/python2.7/site-packages/twext/enterprise/adbapi2.py", line 230, in _reallyExecSQL
	    self._cursor.execute(sql, args)
	  File "/usr/lib64/python2.7/site-packages/txdav/base/datastore/dbapiclient.py", line 76, in execute
	    self.realCursor.execute(sql, args)
	  File "/usr/lib64/python2.7/site-packages/pgdb.py", line 259, in execute
	    self.executemany(operation, (params,))
	  File "/usr/lib64/python2.7/site-packages/pgdb.py", line 289, in executemany
	    raise DatabaseError("error '%s' in '%s'" % (msg, sql))
	pg.DatabaseError: error 'FEHLER:  Constraint »attachment_dropbox_id_path_key« von Relation »attachment« existiert nicht
	' in 'alter table ATTACHMENT
	 drop constraint ATTACHMENT_DROPBOX_ID_PATH_KEY,
	 add primary key(DROPBOX_ID, PATH)'