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/sslutil.py

@@ -628,7 +628,7 b' def wrapserversocket('
     # Otherwise, use the list of more secure ciphers if found in the ssl module.
     if exactprotocol:
         sslcontext.set_ciphers('DEFAULT:@SECLEVEL=0')
-    elif util.safehasattr(ssl, b'_RESTRICTED_SERVER_CIPHERS'):
+    elif util.safehasattr(ssl, '_RESTRICTED_SERVER_CIPHERS'):
         sslcontext.options |= getattr(ssl, 'OP_CIPHER_SERVER_PREFERENCE', 0)
         # pytype: disable=module-attr
         sslcontext.set_ciphers(ssl._RESTRICTED_SERVER_CIPHERS)