cubicweb-squareui #4542740 template is incompatible with left/right components written using cwtags [validation pending]

cwtags monkeypatches CubicWeb's UStringIO so that UStringIO.write() works with cwtags objects. However, squareui uses a list in nav_column(). cwtags objects break the unicode.join() done at the end.

prioritynormal
typebug
done in0.3.7
load0.500
load left0.000
closed by#1eb85791a7fa [basetemplate] Use a proper UStringIO instead of a simple list for components (closes #4542740)
patch[basetemplate] Use a proper UStringIO instead of a simple list for components (closes #4542740) [applied]