setup: bump sqlalchemy minimum version to 1.2.9 to get rid of py3 warning

Avoid verbose warning:

build/minimum-dependency-versions-venv/lib/python3.7/site-packages/sqlalchemy/util/langhelpers.py:637
  .../site-packages/sqlalchemy/util/langhelpers.py:637: DeprecationWarning: `formatargspec` is deprecated since Python 3.5. Use `signature` and the `Signature` object directly
    d_args = inspect.formatargspec(spec[0][1:])

setup.py

@@ -50,7 +50,7 b' requirements = ['
     "Beaker >= 1.10.1, < 2",
     "WebHelpers2 >= 2.0, < 2.1",
     "FormEncode >= 1.3.1, < 1.4",
-    "SQLAlchemy >= 1.1, < 1.4",
+    "SQLAlchemy >= 1.2.9, < 1.4",
     "Mako >= 0.9.1, < 1.1",
     "Pygments >= 2.2.0, < 2.5",
     "Whoosh >= 2.7.1, < 2.8",