Error dumping Python source with assignment where value contains format directive

[luser]

This source:

import ast, meta
m = ast.parse("x = '{y}'")
meta.dump_python_source(m)

Produces this error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/build/autoconftopython/venv/local/lib/python2.7/site-packages/meta-development-py2.7.egg/meta/asttools/visitors/pysourcegen.py", line 873, in dump_python_source
    gen.visit(ast)
  File "/build/autoconftopython/venv/local/lib/python2.7/site-packages/meta-development-py2.7.egg/meta/asttools/visitors/__init__.py", line 44, in visit
    return mehtod(node, *args, **kwargs)
  File "/build/autoconftopython/venv/local/lib/python2.7/site-packages/meta-development-py2.7.egg/meta/asttools/visitors/pysourcegen.py", line 526, in visitModule
    self.visit(node)
  File "/build/autoconftopython/venv/local/lib/python2.7/site-packages/meta-development-py2.7.egg/meta/asttools/visitors/__init__.py", line 44, in visit
    return mehtod(node, *args, **kwargs)
  File "/build/autoconftopython/venv/local/lib/python2.7/site-packages/meta-development-py2.7.egg/meta/asttools/visitors/pysourcegen.py", line 578, in visitAssign
    self.print('{targets} = {value:node}\n', targets=' = '.join(targets), value=node.value)
  File "/build/autoconftopython/venv/local/lib/python2.7/site-packages/meta-development-py2.7.egg/meta/asttools/visitors/pysourcegen.py", line 83, in print
    line = self.formatter.format(line, *args, **kwargs)
  File "/usr/lib/python2.7/string.py", line 545, in format
    return self.vformat(format_string, args, kwargs)
  File "/usr/lib/python2.7/string.py", line 549, in vformat
    result = self._vformat(format_string, args, kwargs, used_args, 2)
  File "/usr/lib/python2.7/string.py", line 582, in _vformat
    result.append(self.format_field(obj, format_spec))
  File "/build/autoconftopython/venv/local/lib/python2.7/site-packages/meta-development-py2.7.egg/meta/asttools/visitors/pysourcegen.py", line 27, in format_field
    gen.visit(value)
  File "/build/autoconftopython/venv/local/lib/python2.7/site-packages/meta-development-py2.7.egg/meta/asttools/visitors/__init__.py", line 44, in visit
    return mehtod(node, *args, **kwargs)
  File "/build/autoconftopython/venv/local/lib/python2.7/site-packages/meta-development-py2.7.egg/meta/asttools/visitors/pysourcegen.py", line 229, in visitStr
    self.print(repr(node.s))
  File "/build/autoconftopython/venv/local/lib/python2.7/site-packages/meta-development-py2.7.egg/meta/asttools/visitors/pysourcegen.py", line 83, in print
    line = self.formatter.format(line, *args, **kwargs)
  File "/usr/lib/python2.7/string.py", line 545, in format
    return self.vformat(format_string, args, kwargs)
  File "/usr/lib/python2.7/string.py", line 549, in vformat
    result = self._vformat(format_string, args, kwargs, used_args, 2)
  File "/usr/lib/python2.7/string.py", line 571, in _vformat
    obj, arg_used = self.get_field(field_name, args, kwargs)
  File "/usr/lib/python2.7/string.py", line 632, in get_field
    obj = self.get_value(first, args, kwargs)
  File "/build/autoconftopython/venv/local/lib/python2.7/site-packages/meta-development-py2.7.egg/meta/asttools/visitors/pysourcegen.py", line 42, in get_value
    key = int(key)
ValueError: invalid literal for int() with base 10: 'y'

This is using current git master 32eccb4

A simpler snippet works:

m = ast.parse("'{y}'")
meta.dump_python_source(m)

produces:

"\n'''{y}\n'''\n\n\n\n\n"