safehasattr: pass attribute name as string instead of bytes

This is a step toward replacing `util.safehasattr` usage with plain `hasattr`.
The builtin function behave poorly in Python2 but this was fixed in Python3.

These change are done one by one as they tend to have a small odd to trigger
puzzling breackage.

mercurial/dispatch.py

@@ -1024,7 +1024,7 b' def _checkshellalias(lui, ui, args):'
     cmd = aliases[0]
     fn = entry[0]
 
-    if cmd and util.safehasattr(fn, b'shell'):
+    if cmd and util.safehasattr(fn, 'shell'):
         # shell alias shouldn't receive early options which are consumed by hg
         _earlyopts, args = _earlysplitopts(args)
         d = lambda: fn(ui, *args[1:])