stack: Update global dependency versions

- Bump patsy to 0.5.6

stack/slapos.cfg

@@ -300,7 +300,7 @@ parso = 0.7.1
 passlib = 1.7.4
 pathlib2 = 2.3.5
 pathspec = 0.12.1:whl
-patsy = 0.5.3
+patsy = 0.5.6
 pbr = 5.9.0
 pexpect = 4.8.0
 pickleshare = 0.7.4