[dak/master] Work with newer SQLAlchemy versions

[Ansgar Burchardt <ansgar@debian.org>]

Newer SQLAlchemy versions seem to track the `binary` attribute of
`BinaryMetadata`.  This means the association proxy in `DBBinary`
would first create a `BinaryMetadata` with `binary` set to `None`,
flush this to the database and then set the actual value of `binary`
we want.  However the flush fails, as `NULL` is not allowed for the
`binary_id` column.

The problem can be avoided by not setting `binary` to `None`.  This is
treated as an "undefined value" by SQLAlchemy and changing it later
means the database row never sees `NULL`.

The same applies to the `source` attribute of `SourceMetadata`.
---
 daklib/dbconn.py | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/daklib/dbconn.py b/daklib/dbconn.py
index 3a7f55b..3d3561f 100755
--- a/daklib/dbconn.py
+++ b/daklib/dbconn.py
@@ -2158,7 +2158,8 @@ class BinaryMetadata(ORMObject):
     def __init__(self, key = None, value = None, binary = None):
         self.key = key
         self.value = value
-        self.binary = binary
+        if binary is not None:
+            self.binary = binary
 
     def properties(self):
         return ['binary', 'key', 'value']
@@ -2174,7 +2175,8 @@ class SourceMetadata(ORMObject):
     def __init__(self, key = None, value = None, source = None):
         self.key = key
         self.value = value
-        self.source = source
+        if source is not None:
+            self.source = source
 
     def properties(self):
         return ['source', 'key', 'value']
-- 
2.1.4