ui: avoid needless casting to a str

In many cases, we don't need to cast to a str because the object will
be cast when it is eventually written.

As part of testing this, I added some code to raise exceptions when a
non-str was passed in and wasn't able to trigger it. i.e. we're already
passing str into this function everywhere, so the casting isn't
necessary.

hgext/color.py

@@ -434,16 +434,15 b' class colorui(uimod.ui):'
         label = opts.get('label', '')
         if self._buffers:
             if self._bufferapplylabels:
-                self._buffers[-1].extend(self.label(str(a), label)
-                                         for a in args)
+                self._buffers[-1].extend(self.label(a, label) for a in args)
             else:
-                self._buffers[-1].extend(str(a) for a in args)
+                self._buffers[-1].extend(args)
         elif self._colormode == 'win32':
             for a in args:
                 win32print(a, super(colorui, self).write, **opts)
         else:
             return super(colorui, self).write(
-                *[self.label(str(a), label) for a in args], **opts)
+                *[self.label(a, label) for a in args], **opts)
 
     def write_err(self, *args, **opts):
         if self._colormode is None:
@@ -457,7 +456,7 b' class colorui(uimod.ui):'
                 win32print(a, super(colorui, self).write_err, **opts)
         else:
             return super(colorui, self).write_err(
-                *[self.label(str(a), label) for a in args], **opts)
+                *[self.label(a, label) for a in args], **opts)
 
     def showlabel(self, msg, label):
         if label and msg:

mercurial/ui.py

@@ -622,11 +622,11 b' class ui(object):'
         a label of "status.modified" for modified files.
         '''
         if self._buffers:
-            self._buffers[-1].extend([str(a) for a in args])
+            self._buffers[-1].extend(a for a in args)
         else:
             self._progclear()
             for a in args:
-                self.fout.write(str(a))
+                self.fout.write(a)
 
     def write_err(self, *args, **opts):
         self._progclear()
@@ -636,7 +636,7 b' class ui(object):'
             if not getattr(self.fout, 'closed', False):
                 self.fout.flush()
             for a in args:
-                self.ferr.write(str(a))
+                self.ferr.write(a)
             # stderr may be buffered under win32 when redirected to files,
             # including stdout.
             if not getattr(self.ferr, 'closed', False):