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/crecord.py

@@ -573,7 +573,7 b' def chunkselector(ui, headerlist, operat'
     ui.write(_(b'starting interactive selection\n'))
     chunkselector = curseschunkselector(headerlist, ui, operation)
     origsigtstp = sentinel = object()
-    if util.safehasattr(signal, b'SIGTSTP'):
+    if util.safehasattr(signal, 'SIGTSTP'):
         origsigtstp = signal.getsignal(signal.SIGTSTP)
     try:
         with util.with_lc_ctype():