translation failure with rpython in default branch of pypy but success with py3.6 branch

As I'm trying to translate [cycy](https://github.com/DeloitteHux/cycy), first I used rpython in default branch of the cloned pypy source, ending in this error:
```
(py27) Xuans-MBP:cycy xuanwu$ python ~/git/pypy/rpython/bin/rpython cycy/target.py
[translation:info] 2.7.17 |Anaconda, Inc.| (default, Oct 21 2019, 14:10:59)
[GCC 4.2.1 Compatible Clang 4.0.1 (tags/RELEASE_401/final)]
[platform:msg] Set platform with 'host' cc=None, using cc='clang -arch x86_64', version='Unknown'
[translation:info] Translating target as defined by cycy/target
/Users/xuanwu/git/cycy/cycy/parser/core.py:507: ParserGeneratorWarning: 184 shift/reduce conflicts
_parser = _pg.build()
/Users/xuanwu/git/cycy/cycy/parser/core.py:507: ParserGeneratorWarning: 30 reduce/reduce conflicts
_parser = _pg.build()
[translation] translate.py configuration:
[translation] [translate]
targetspec = cycy/target
[translation] translation configuration:
[translation] [translation]
gc = incminimark
gctransformer = framework
list_comprehension_operations = True
withsmallfuncsets = 5
[translation:info] Annotating&simplifying...
[f7] {translation-task
starting annotate
[translation:info] with policy: rpython.annotator.policy.AnnotatorPolicy
.....++++++++++++++****************************%%%%%%%%%%%%%%%%%%%%%###%########%%%#####################################%%%%%%%%%%%%###%***************
..++++++++++++++****[1b6] translation-task}

[Timer] Timings:
[Timer] annotate --- 3.5 s
[Timer] ========================================
[Timer] Total: --- 3.5 s
[translation:info] Error:
File "/Users/xuanwu/git/pypy/rpython/translator/goal/translate.py", line 318, in main
drv.proceed(goals)
File "/Users/xuanwu/git/pypy/rpython/translator/driver.py", line 555, in proceed
result = self._execute(goals, task_skip = self._maybe_skip())
File "/Users/xuanwu/git/pypy/rpython/translator/tool/taskengine.py", line 114, in _execute
res = self._do(goal, taskcallable, *args, **kwds)
File "/Users/xuanwu/git/pypy/rpython/translator/driver.py", line 278, in _do
res = func()
File "/Users/xuanwu/git/pypy/rpython/translator/driver.py", line 315, in task_annotate
s = annotator.build_types(self.entry_point, self.inputtypes)
File "/Users/xuanwu/git/pypy/rpython/annotator/annrpython.py", line 92, in build_types
return self.build_graph_types(flowgraph, inputs_s, complete_now=complete_now)
File "/Users/xuanwu/git/pypy/rpython/annotator/annrpython.py", line 140, in build_graph_types
self.complete()
File "/Users/xuanwu/git/pypy/rpython/annotator/annrpython.py", line 229, in complete
self.complete_pending_blocks()
File "/Users/xuanwu/git/pypy/rpython/annotator/annrpython.py", line 224, in complete_pending_blocks
self.processblock(graph, block)
File "/Users/xuanwu/git/pypy/rpython/annotator/annrpython.py", line 398, in processblock
self.flowin(graph, block)
File "/Users/xuanwu/git/pypy/rpython/annotator/annrpython.py", line 501, in flowin
self.consider_op(op)
File "/Users/xuanwu/git/pypy/rpython/annotator/annrpython.py", line 653, in consider_op
resultcell = op.consider(self)
File "/Users/xuanwu/git/pypy/rpython/flowspace/operation.py", line 104, in consider
return spec(annotator, *self.args)
File "/Users/xuanwu/git/pypy/rpython/annotator/unaryop.py", line 118, in simple_call_SomeObject
return s_func.call(argspec)
File "/Users/xuanwu/git/pypy/rpython/annotator/unaryop.py", line 978, in call
return bookkeeper.pbc_call(self, args)
File "/Users/xuanwu/git/pypy/rpython/annotator/bookkeeper.py", line 535, in pbc_call
results.append(desc.pycall(whence, args, s_previous_result, op))
File "/Users/xuanwu/git/pypy/rpython/annotator/classdesc.py", line 732, in pycall
s_init.call(args)
File "/Users/xuanwu/git/pypy/rpython/annotator/unaryop.py", line 978, in call
return bookkeeper.pbc_call(self, args)
File "/Users/xuanwu/git/pypy/rpython/annotator/bookkeeper.py", line 535, in pbc_call
results.append(desc.pycall(whence, args, s_previous_result, op))
File "/Users/xuanwu/git/pypy/rpython/annotator/description.py", line 284, in pycall
inputcells = self.parse_arguments(args)
File "/Users/xuanwu/git/pypy/rpython/annotator/description.py", line 269, in parse_arguments
(self.name, e.getmsg()))
[translation:ERROR] AnnotatorError:

signature mismatch: __init__() takes exactly 4 arguments (5 given)

Occurred processing the following simple_call:
function StrMatchContext.__init__ returning

ctx_0 = simple_call((type StrMatchContext), s_0, pos_0, v6, v7)

In :
Happened at file /opt/miniconda3/envs/py27/lib/python2.7/site-packages/rply/lexergenerator.py line 36

==> ctx = rsre_core.StrMatchContext(s, pos, len(s), self.flags)

matched = rsre_core.match_context(ctx, self._pattern)
if matched:

Known variable annotations:
s_0 = SomeString(no_nul=True)
pos_0 = SomeInteger(const=0, knowntype=int, nonneg=True, unsigned=False)
v6 = SomeInteger(knowntype=int, nonneg=True, unsigned=False)
v7 = SomeInteger(const=0, knowntype=int, nonneg=True, unsigned=False)

Processing block:
block@101[pos_0...] is a
in (rply.lexergenerator:30)matches
containing the following operations:
v6 = len(s_0)
v7 = getattr(self_0, ('flags'))
ctx_0 = simple_call((type StrMatchContext), s_0, pos_0, v6, v7)
v8 = getattr(self_0, ('_pattern'))
matched_0 = simple_call((function match_context), ctx_0, v8)
v9 = bool(matched_0)
--end--
[translation] start debugger...
> /Users/xuanwu/git/pypy/rpython/annotator/description.py(269)parse_arguments()
-> (self.name, e.getmsg()))
```

Then I switched to py3.6 branch with `$ hg update py3.6` in pypy source path, and succeeded to translate.

Being new to both pypy and rply, I wonder what's the difference of rpython between these two branches?

Thanks.