Fix urwid > 2.4.2 compatibility

`Columns` cannot make `pack` with FLOW logic
on FIXED-only widgets since no `rows` method is expected.

Render of `FixedButton` and `FixedRadioButton`
previously worked only due to the nonexistent validation
(FIXED-only widgets support was not implemented
and FLOW logic called explicit)

Change-Id: Iaa1cdded7362c95f60d8073c7edc78fdac1ead14

gertty/mywid.py

@@ -48,17 +48,23 @@ class TextButton(urwid.Button):
         self._w = urwid.AttrMap(self.text, None, focus_map='focused')
 
 class FixedButton(urwid.Button):
+    # todo(Aleksei): This class is not needed with urwid 2.5.0+  (WIMP is already Flow/Fixed)
     def sizing(self):
-        return frozenset([urwid.FIXED])
+        return frozenset((urwid.FLOW, urwid.FIXED))
 
     def pack(self, size, focus=False):
+        if size:
+            return super(FixedButton, self).pack(size, focus)
         return (len(self.get_label())+4, 1)
 
 class FixedRadioButton(urwid.RadioButton):
+    # todo(Aleksei): This class is not needed with urwid 2.5.0+  (WIMP is already Flow/Fixed)
     def sizing(self):
-        return frozenset([urwid.FIXED])
+        return frozenset((urwid.FLOW, urwid.FIXED))
 
     def pack(self, size, focus=False):
+        if size:
+            return super(FixedButton, self).pack(size, focus)
         return (len(self.get_label())+4, 1)
 
 class TableColumn(urwid.Pile):

requirements.txt

@@ -1,6 +1,6 @@
 pbr>=0.11
 
-urwid>=1.2.1,!=1.3.0
+urwid>=2.0.0
 SQLAlchemy>=1.4
 GitPython>=0.3.7
 python-dateutil