revsetlang: raise ParseError to report invalid format character

It's more common in revset and templater than raising Abort.

I have a couple more patches to address exceptions caused by bad format string
passed to revset() template function.

mercurial/revsetlang.py

@@ -641,7 +641,8 b' def formatspec(expr, *args):'
             d = expr[pos]
             ret.append(listexp(list(next(argiter)), d))
         else:
-            raise error.Abort(_('unexpected revspec format character %s') % d)
+            raise error.ParseError(_('unexpected revspec format character %s')
+                                   % d)
         pos += 1
 
     return ''.join(ret)

tests/test-command-template.t

@@ -4080,6 +4080,12 b' default. join() should agree with the de'
   5:13207e5a10d9fd28ec424934298e176197f2c67f,
   4:bbe44766e73d5f11ed2177f1838de10c53ef3e74
 
+Invalid arguments passed to revset()
+
+  $ hg log -T '{revset("%whatever", 0)}\n'
+  hg: parse error: unexpected revspec format character w
+  [255]
+
 Test files function
 
   $ hg log -T "{rev}\n{join(files('*'), '\n')}\n"