Segfault in test_conv_annual (test_period.py , when running nosetests)
This happened with the current Pandas on an EC2 machine (Amazon Linux/ Debian squeeze).

I attached the gdb trace. Unfortunately I don't understand what's going on but maybe somebody else does.

```
(gdb) run test_period.py
Starting program: /usr/local/bin/python test_period.py
[Thread debugging using libthread_db enabled]
nose.config: INFO: Ignoring files matching ['^\\.', '^_', '^setup\\.py$']
test_conv_annual (__main__.TestFreqConversion) ... 
Program received signal SIGSEGV, Segmentation fault.
0x00007ffff6dde819 in free () from /lib/libc.so.6
(gdb) where
#0  0x00007ffff6dde819 in free () from /lib/libc.so.6
#1  0x00007ffff28659ee in skts_strftime (ordinal=148, freq=2000, 
    args=0x1f97300) at pandas/src/period.c:1234
#2  0x00007ffff2865fc1 in period_to_string (value=148, freq=2000)
    at pandas/src/period.c:1333
#3  0x00007ffff26e2395 in __pyx_pf_6pandas_3lib_120period_ordinal_to_string (
    __pyx_self=0x0, __pyx_v_value=148, __pyx_v_freq=2000)
    at pandas/src/tseries.c:48155
#4  0x00007ffff26e2339 in __pyx_pw_6pandas_3lib_121period_ordinal_to_string (
    __pyx_self=0x0, __pyx_args=0x1f599c0, __pyx_kwds=0x0)
    at pandas/src/tseries.c:48123
#5  0x00007ffff7a232d9 in PyCFunction_Call (func=0x15c7d08, arg=0x1f599c0, 
    kw=0x0) at Objects/methodobject.c:85
#6  0x00007ffff7aca504 in call_function (pp_stack=0x7fffffff6420, oparg=2)
    at Python/ceval.c:4021
#7  0x00007ffff7ac4e9e in PyEval_EvalFrameEx (f=0x2078090, throwflag=0)
    at Python/ceval.c:2666
#8  0x00007ffff7ac79ba in PyEval_EvalCodeEx (co=0x1648ca0, globals=0x16e6ba0, 
    locals=0x0, args=0x1f97248, argcount=1, kws=0x0, kwcount=0, defs=0x0, 
    defcount=0, closure=0x0) at Python/ceval.c:3253
#9  0x00007ffff79ff7a1 in function_call (func=0x137e990, arg=0x1f97220, kw=0x0)
    at Objects/funcobject.c:526
#10 0x00007ffff79c0453 in PyObject_Call (func=0x137e990, arg=0x1f97220, kw=0x0)
---Type <return> to continue, or q <return> to quit---
    at Objects/abstract.c:2529
#11 0x00007ffff79dc87c in instancemethod_call (func=0x137e990, arg=0x1f97220, 
    kw=0x0) at Objects/classobject.c:2578
#12 0x00007ffff79c0453 in PyObject_Call (func=0x1f95860, arg=0x7ffff7fa7060, 
    kw=0x0) at Objects/abstract.c:2529
#13 0x00007ffff7ac9bf5 in PyEval_CallObjectWithKeywords (func=0x1f95860, 
    arg=0x7ffff7fa7060, kw=0x0) at Python/ceval.c:3890
#14 0x00007ffff7a605ad in slot_tp_repr (self=0x2038300)
    at Objects/typeobject.c:5326
#15 0x00007ffff7a24f82 in PyObject_Repr (v=0x2038300) at Objects/object.c:381
#16 0x00007ffff7ab90d8 in builtin_repr (self=0x0, v=0x2038300)
    at Python/bltinmodule.c:2139
#17 0x00007ffff7aca2c2 in call_function (pp_stack=0x7fffffff6d20, oparg=1)
    at Python/ceval.c:4009
#18 0x00007ffff7ac4e9e in PyEval_EvalFrameEx (f=0x2077e40, throwflag=0)
    at Python/ceval.c:2666
#19 0x00007ffff7ac79ba in PyEval_EvalCodeEx (co=0xa991a0, globals=0xadced0, 
    locals=0x0, args=0x2077d90, argcount=2, kws=0x2077da0, kwcount=0, 
    defs=0xaa0d08, defcount=3, closure=0x0) at Python/ceval.c:3253
#20 0x00007ffff7acab78 in fast_function (func=0xaaaed0, 
    pp_stack=0x7fffffff7240, n=2, na=2, nk=0) at Python/ceval.c:4117
#21 0x00007ffff7aca704 in call_function (pp_stack=0x7fffffff7240, oparg=2)
    at Python/ceval.c:4042
---Type <return> to continue, or q <return> to quit---
#22 0x00007ffff7ac4e9e in PyEval_EvalFrameEx (f=0x2077bc0, throwflag=0)
    at Python/ceval.c:2666
#23 0x00007ffff7ac79ba in PyEval_EvalCodeEx (co=0xf0b7d0, globals=0xd26c20, 
    locals=0x0, args=0x2036308, argcount=2, kws=0x2036318, kwcount=0, 
    defs=0xf182b8, defcount=1, closure=0x0) at Python/ceval.c:3253
#24 0x00007ffff7acab78 in fast_function (func=0xf163a8, 
    pp_stack=0x7fffffff7760, n=2, na=2, nk=0) at Python/ceval.c:4117
#25 0x00007ffff7aca704 in call_function (pp_stack=0x7fffffff7760, oparg=2)
    at Python/ceval.c:4042
#26 0x00007ffff7ac4e9e in PyEval_EvalFrameEx (f=0x20360a0, throwflag=0)
    at Python/ceval.c:2666
#27 0x00007ffff7acaa47 in fast_function (func=0x19c54f8, 
    pp_stack=0x7fffffff7b00, n=1, na=1, nk=0) at Python/ceval.c:4107
#28 0x00007ffff7aca704 in call_function (pp_stack=0x7fffffff7b00, oparg=0)
    at Python/ceval.c:4042
#29 0x00007ffff7ac4e9e in PyEval_EvalFrameEx (f=0x20340e0, throwflag=0)
    at Python/ceval.c:2666
#30 0x00007ffff7ac79ba in PyEval_EvalCodeEx (co=0xfd2670, globals=0xfc2110, 
    locals=0x0, args=0x1f553d0, argcount=2, kws=0x7ffff7fa7088, kwcount=0, 
    defs=0xfff638, defcount=1, closure=0x0) at Python/ceval.c:3253
#31 0x00007ffff79ff7a1 in function_call (func=0x1006798, arg=0x1f553a8, 
    kw=0x2033830) at Objects/funcobject.c:526
#32 0x00007ffff79c0453 in PyObject_Call (func=0x1006798, arg=0x1f553a8, 
---Type <return> to continue, or q <return> to quit---
    kw=0x2033830) at Objects/abstract.c:2529
#33 0x00007ffff7acbaf6 in ext_do_call (func=0x1006798, 
    pp_stack=0x7fffffff8038, flags=3, na=1, nk=0) at Python/ceval.c:4334
#34 0x00007ffff7ac5101 in PyEval_EvalFrameEx (f=0x2033ed0, throwflag=0)
    at Python/ceval.c:2705
#35 0x00007ffff7ac79ba in PyEval_EvalCodeEx (co=0xfd2880, globals=0xfc2110, 
    locals=0x0, args=0x1f50d30, argcount=2, kws=0x0, kwcount=0, defs=0x0, 
    defcount=0, closure=0x0) at Python/ceval.c:3253
#36 0x00007ffff79ff7a1 in function_call (func=0x10068e8, arg=0x1f50d08, kw=0x0)
    at Objects/funcobject.c:526
#37 0x00007ffff79c0453 in PyObject_Call (func=0x10068e8, arg=0x1f50d08, kw=0x0)
    at Objects/abstract.c:2529
#38 0x00007ffff79dc87c in instancemethod_call (func=0x10068e8, arg=0x1f50d08, 
    kw=0x0) at Objects/classobject.c:2578
#39 0x00007ffff79c0453 in PyObject_Call (func=0x1d50560, arg=0x1f974c0, kw=0x0)
    at Objects/abstract.c:2529
#40 0x00007ffff7a60a91 in slot_tp_call (self=0x1f97c30, args=0x1f974c0, 
    kwds=0x0) at Objects/typeobject.c:5403
#41 0x00007ffff79c0453 in PyObject_Call (func=0x1f97c30, arg=0x1f974c0, kw=0x0)
    at Objects/abstract.c:2529
#42 0x00007ffff7acb42b in do_call (func=0x1f97c30, pp_stack=0x7fffffff8970, 
    na=1, nk=0) at Python/ceval.c:4239
#43 0x00007ffff7aca726 in call_function (pp_stack=0x7fffffff8970, oparg=1)
---Type <return> to continue, or q <return> to quit---
    at Python/ceval.c:4044
#44 0x00007ffff7ac4e9e in PyEval_EvalFrameEx (f=0x2033b70, throwflag=0)
    at Python/ceval.c:2666
#45 0x00007ffff7acaa47 in fast_function (func=0x1ce8450, 
    pp_stack=0x7fffffff8d10, n=2, na=2, nk=0) at Python/ceval.c:4107
#46 0x00007ffff7aca704 in call_function (pp_stack=0x7fffffff8d10, oparg=1)
    at Python/ceval.c:4042
#47 0x00007ffff7ac4e9e in PyEval_EvalFrameEx (f=0x2032d10, throwflag=0)
    at Python/ceval.c:2666
#48 0x00007ffff7ac79ba in PyEval_EvalCodeEx (co=0x1ce00f0, globals=0x1d15470, 
    locals=0x0, args=0x1d3c6a0, argcount=2, kws=0x7ffff7fa7088, kwcount=0, 
    defs=0x0, defcount=0, closure=0x0) at Python/ceval.c:3253
#49 0x00007ffff79ff7a1 in function_call (func=0x1ce83a8, arg=0x1d3c678, 
    kw=0x2032230) at Objects/funcobject.c:526
#50 0x00007ffff79c0453 in PyObject_Call (func=0x1ce83a8, arg=0x1d3c678, 
    kw=0x2032230) at Objects/abstract.c:2529
#51 0x00007ffff7acbaf6 in ext_do_call (func=0x1ce83a8, 
    pp_stack=0x7fffffff9248, flags=3, na=1, nk=0) at Python/ceval.c:4334
#52 0x00007ffff7ac5101 in PyEval_EvalFrameEx (f=0x2032b00, throwflag=0)
    at Python/ceval.c:2705
#53 0x00007ffff7ac79ba in PyEval_EvalCodeEx (co=0x1ccfa90, globals=0x1d15470, 
    locals=0x0, args=0x1f762e0, argcount=2, kws=0x0, kwcount=0, defs=0x0, 
    defcount=0, closure=0x0) at Python/ceval.c:3253
---Type <return> to continue, or q <return> to quit---
#54 0x00007ffff79ff7a1 in function_call (func=0x1cd6d80, arg=0x1f762b8, kw=0x0)
    at Objects/funcobject.c:526
#55 0x00007ffff79c0453 in PyObject_Call (func=0x1cd6d80, arg=0x1f762b8, kw=0x0)
    at Objects/abstract.c:2529
#56 0x00007ffff79dc87c in instancemethod_call (func=0x1cd6d80, arg=0x1f762b8, 
    kw=0x0) at Objects/classobject.c:2578
#57 0x00007ffff79c0453 in PyObject_Call (func=0x1f86960, arg=0x1f975a0, kw=0x0)
    at Objects/abstract.c:2529
#58 0x00007ffff7a60a91 in slot_tp_call (self=0x1f97e60, args=0x1f975a0, 
    kwds=0x0) at Objects/typeobject.c:5403
#59 0x00007ffff79c0453 in PyObject_Call (func=0x1f97e60, arg=0x1f975a0, kw=0x0)
    at Objects/abstract.c:2529
#60 0x00007ffff7acb42b in do_call (func=0x1f97e60, pp_stack=0x7fffffff9b80, 
    na=1, nk=0) at Python/ceval.c:4239
#61 0x00007ffff7aca726 in call_function (pp_stack=0x7fffffff9b80, oparg=1)
    at Python/ceval.c:4044
#62 0x00007ffff7ac4e9e in PyEval_EvalFrameEx (f=0x2031c70, throwflag=0)
    at Python/ceval.c:2666
#63 0x00007ffff7ac79ba in PyEval_EvalCodeEx (co=0x1cefbf0, globals=0x1d16290, 
    locals=0x0, args=0x1f76100, argcount=2, kws=0x7ffff7fa7088, kwcount=0, 
    defs=0x0, defcount=0, closure=0x0) at Python/ceval.c:3253
#64 0x00007ffff79ff7a1 in function_call (func=0x1d27ed0, arg=0x1f760d8, 
    kw=0x20308e0) at Objects/funcobject.c:526
---Type <return> to continue, or q <return> to quit---
#65 0x00007ffff79c0453 in PyObject_Call (func=0x1d27ed0, arg=0x1f760d8, 
    kw=0x20308e0) at Objects/abstract.c:2529
#66 0x00007ffff7acbaf6 in ext_do_call (func=0x1d27ed0, 
    pp_stack=0x7fffffffa0b8, flags=3, na=1, nk=0) at Python/ceval.c:4334
#67 0x00007ffff7ac5101 in PyEval_EvalFrameEx (f=0x2031a60, throwflag=0)
    at Python/ceval.c:2705
#68 0x00007ffff7ac79ba in PyEval_EvalCodeEx (co=0x1cef930, globals=0x1d16290, 
    locals=0x0, args=0x1f76358, argcount=2, kws=0x0, kwcount=0, defs=0x0, 
    defcount=0, closure=0x0) at Python/ceval.c:3253
#69 0x00007ffff79ff7a1 in function_call (func=0x1d27cd8, arg=0x1f76330, kw=0x0)
    at Objects/funcobject.c:526
#70 0x00007ffff79c0453 in PyObject_Call (func=0x1d27cd8, arg=0x1f76330, kw=0x0)
    at Objects/abstract.c:2529
#71 0x00007ffff79dc87c in instancemethod_call (func=0x1d27cd8, arg=0x1f76330, 
    kw=0x0) at Objects/classobject.c:2578
#72 0x00007ffff79c0453 in PyObject_Call (func=0x1f86560, arg=0x1f976f0, kw=0x0)
    at Objects/abstract.c:2529
#73 0x00007ffff7a60a91 in slot_tp_call (self=0x1f97ca0, args=0x1f976f0, 
    kwds=0x0) at Objects/typeobject.c:5403
#74 0x00007ffff79c0453 in PyObject_Call (func=0x1f97ca0, arg=0x1f976f0, kw=0x0)
    at Objects/abstract.c:2529
#75 0x00007ffff7acb42b in do_call (func=0x1f97ca0, pp_stack=0x7fffffffa9f0, 
    na=1, nk=0) at Python/ceval.c:4239
---Type <return> to continue, or q <return> to quit---
#76 0x00007ffff7aca726 in call_function (pp_stack=0x7fffffffa9f0, oparg=1)
    at Python/ceval.c:4044
#77 0x00007ffff7ac4e9e in PyEval_EvalFrameEx (f=0x20312a0, throwflag=0)
    at Python/ceval.c:2666
#78 0x00007ffff7ac79ba in PyEval_EvalCodeEx (co=0x1cefbf0, globals=0x1d16290, 
    locals=0x0, args=0x1f76268, argcount=2, kws=0x7ffff7fa7088, kwcount=0, 
    defs=0x0, defcount=0, closure=0x0) at Python/ceval.c:3253
#79 0x00007ffff79ff7a1 in function_call (func=0x1d27ed0, arg=0x1f76240, 
    kw=0x2030790) at Objects/funcobject.c:526
#80 0x00007ffff79c0453 in PyObject_Call (func=0x1d27ed0, arg=0x1f76240, 
    kw=0x2030790) at Objects/abstract.c:2529
#81 0x00007ffff7acbaf6 in ext_do_call (func=0x1d27ed0, 
    pp_stack=0x7fffffffaf28, flags=3, na=1, nk=0) at Python/ceval.c:4334
#82 0x00007ffff7ac5101 in PyEval_EvalFrameEx (f=0x2031090, throwflag=0)
    at Python/ceval.c:2705
#83 0x00007ffff7ac79ba in PyEval_EvalCodeEx (co=0x1cef930, globals=0x1d16290, 
    locals=0x0, args=0x1f43cb8, argcount=2, kws=0x0, kwcount=0, defs=0x0, 
    defcount=0, closure=0x0) at Python/ceval.c:3253
#84 0x00007ffff79ff7a1 in function_call (func=0x1d27cd8, arg=0x1f43c90, kw=0x0)
    at Objects/funcobject.c:526
#85 0x00007ffff79c0453 in PyObject_Call (func=0x1d27cd8, arg=0x1f43c90, kw=0x0)
    at Objects/abstract.c:2529
#86 0x00007ffff79dc87c in instancemethod_call (func=0x1d27cd8, arg=0x1f43c90, 
---Type <return> to continue, or q <return> to quit---
    kw=0x0) at Objects/classobject.c:2578
#87 0x00007ffff79c0453 in PyObject_Call (func=0x1f57f60, arg=0x1f97760, kw=0x0)
    at Objects/abstract.c:2529
#88 0x00007ffff7a60a91 in slot_tp_call (self=0x1fa1ed0, args=0x1f97760, 
    kwds=0x0) at Objects/typeobject.c:5403
#89 0x00007ffff79c0453 in PyObject_Call (func=0x1fa1ed0, arg=0x1f97760, kw=0x0)
    at Objects/abstract.c:2529
#90 0x00007ffff7acb42b in do_call (func=0x1fa1ed0, pp_stack=0x7fffffffb860, 
    na=1, nk=0) at Python/ceval.c:4239
#91 0x00007ffff7aca726 in call_function (pp_stack=0x7fffffffb860, oparg=1)
    at Python/ceval.c:4044
#92 0x00007ffff7ac4e9e in PyEval_EvalFrameEx (f=0x202f280, throwflag=0)
    at Python/ceval.c:2666
#93 0x00007ffff7ac79ba in PyEval_EvalCodeEx (co=0x1cefbf0, globals=0x1d16290, 
    locals=0x0, args=0x1f761f0, argcount=2, kws=0x7ffff7fa7088, kwcount=0, 
    defs=0x0, defcount=0, closure=0x0) at Python/ceval.c:3253
#94 0x00007ffff79ff7a1 in function_call (func=0x1d27ed0, arg=0x1f761c8, 
    kw=0x202f130) at Objects/funcobject.c:526
#95 0x00007ffff79c0453 in PyObject_Call (func=0x1d27ed0, arg=0x1f761c8, 
    kw=0x202f130) at Objects/abstract.c:2529
#96 0x00007ffff7acbaf6 in ext_do_call (func=0x1d27ed0, 
    pp_stack=0x7fffffffbd98, flags=3, na=1, nk=0) at Python/ceval.c:4334
#97 0x00007ffff7ac5101 in PyEval_EvalFrameEx (f=0x202ef20, throwflag=0)
---Type <return> to continue, or q <return> to quit---
    at Python/ceval.c:2705
#98 0x00007ffff7ac79ba in PyEval_EvalCodeEx (co=0x1cef930, globals=0x1d16290, 
    locals=0x0, args=0x1f59f10, argcount=2, kws=0x0, kwcount=0, defs=0x0, 
    defcount=0, closure=0x0) at Python/ceval.c:3253
#99 0x00007ffff79ff7a1 in function_call (func=0x1d27cd8, arg=0x1f59ee8, kw=0x0)
    at Objects/funcobject.c:526
#100 0x00007ffff79c0453 in PyObject_Call (func=0x1d27cd8, arg=0x1f59ee8, 
    kw=0x0) at Objects/abstract.c:2529
#101 0x00007ffff79dc87c in instancemethod_call (func=0x1d27cd8, arg=0x1f59ee8, 
    kw=0x0) at Objects/classobject.c:2578
#102 0x00007ffff79c0453 in PyObject_Call (func=0x1e450e0, arg=0x1d32ca0, 
    kw=0x0) at Objects/abstract.c:2529
#103 0x00007ffff7a60a91 in slot_tp_call (self=0x1f8f990, args=0x1d32ca0, 
    kwds=0x0) at Objects/typeobject.c:5403
#104 0x00007ffff79c0453 in PyObject_Call (func=0x1f8f990, arg=0x1d32ca0, 
    kw=0x0) at Objects/abstract.c:2529
#105 0x00007ffff7acb42b in do_call (func=0x1f8f990, pp_stack=0x7fffffffc6d0, 
    na=1, nk=0) at Python/ceval.c:4239
#106 0x00007ffff7aca726 in call_function (pp_stack=0x7fffffffc6d0, oparg=1)
    at Python/ceval.c:4044
#107 0x00007ffff7ac4e9e in PyEval_EvalFrameEx (f=0x202dec0, throwflag=0)
    at Python/ceval.c:2666
#108 0x00007ffff7acaa47 in fast_function (func=0x1d2c300, 
---Type <return> to continue, or q <return> to quit---
    pp_stack=0x7fffffffca70, n=2, na=2, nk=0) at Python/ceval.c:4107
#109 0x00007ffff7aca704 in call_function (pp_stack=0x7fffffffca70, oparg=1)
    at Python/ceval.c:4042
#110 0x00007ffff7ac4e9e in PyEval_EvalFrameEx (f=0x202d1c0, throwflag=0)
    at Python/ceval.c:2666
#111 0x00007ffff7acaa47 in fast_function (func=0x1d2c648, 
    pp_stack=0x7fffffffce10, n=1, na=1, nk=0) at Python/ceval.c:4107
#112 0x00007ffff7aca704 in call_function (pp_stack=0x7fffffffce10, oparg=0)
    at Python/ceval.c:4042
#113 0x00007ffff7ac4e9e in PyEval_EvalFrameEx (f=0x1d74860, throwflag=0)
    at Python/ceval.c:2666
#114 0x00007ffff7ac79ba in PyEval_EvalCodeEx (co=0x1033460, globals=0xfc4cc0, 
    locals=0x0, args=0x1d32d38, argcount=1, kws=0x1c5be98, kwcount=6, 
    defs=0x1026928, defcount=10, closure=0x0) at Python/ceval.c:3253
#115 0x00007ffff79ff7a1 in function_call (func=0x1055798, arg=0x1d32d10, 
    kw=0x1d6ee60) at Objects/funcobject.c:526
#116 0x00007ffff79c0453 in PyObject_Call (func=0x1055798, arg=0x1d32d10, 
    kw=0x1d6ee60) at Objects/abstract.c:2529
#117 0x00007ffff79dc87c in instancemethod_call (func=0x1055798, arg=0x1d32d10, 
    kw=0x1d6ee60) at Objects/classobject.c:2578
#118 0x00007ffff79c0453 in PyObject_Call (func=0x1d3e760, arg=0x1d32d10, 
    kw=0x1d6ee60) at Objects/abstract.c:2529
#119 0x00007ffff7acbaf6 in ext_do_call (func=0x1d3e760, 
---Type <return> to continue, or q <return> to quit---
    pp_stack=0x7fffffffd628, flags=2, na=1, nk=5) at Python/ceval.c:4334
#120 0x00007ffff7ac5101 in PyEval_EvalFrameEx (f=0x1b06250, throwflag=0)
    at Python/ceval.c:2705
#121 0x00007ffff7ac79ba in PyEval_EvalCodeEx (co=0x19bcca0, globals=0x19f5580, 
    locals=0x0, args=0xf18638, argcount=1, kws=0x1d2f088, kwcount=3, 
    defs=0x1cdbb08, defcount=11, closure=0x0) at Python/ceval.c:3253
#122 0x00007ffff79ff7a1 in function_call (func=0x1d2c3a8, arg=0xf18610, 
    kw=0x1d6dab0) at Objects/funcobject.c:526
#123 0x00007ffff79c0453 in PyObject_Call (func=0x1d2c3a8, arg=0xf18610, 
    kw=0x1d6dab0) at Objects/abstract.c:2529
#124 0x00007ffff79dc87c in instancemethod_call (func=0x1d2c3a8, arg=0xf18610, 
    kw=0x1d6dab0) at Objects/classobject.c:2578
#125 0x00007ffff79c0453 in PyObject_Call (func=0x1d3e6e0, arg=0x7ffff7fa7060, 
    kw=0x1d6dab0) at Objects/abstract.c:2529
#126 0x00007ffff7a61898 in slot_tp_init (self=0x1d32c30, args=0x7ffff7fa7060, 
    kwds=0x1d6dab0) at Objects/typeobject.c:5663
#127 0x00007ffff7a4e3e1 in type_call (type=0x1d67230, args=0x7ffff7fa7060, 
    kwds=0x1d6dab0) at Objects/typeobject.c:737
#128 0x00007ffff79c0453 in PyObject_Call (func=0x1d67230, arg=0x7ffff7fa7060, 
    kw=0x1d6dab0) at Objects/abstract.c:2529
#129 0x00007ffff7acbaf6 in ext_do_call (func=0x1d67230, 
    pp_stack=0x7fffffffdf28, flags=2, na=0, nk=1) at Python/ceval.c:4334
#130 0x00007ffff7ac5101 in PyEval_EvalFrameEx (f=0x1d13e10, throwflag=0)
---Type <return> to continue, or q <return> to quit---
    at Python/ceval.c:2705
#131 0x00007ffff7ac79ba in PyEval_EvalCodeEx (co=0x19cc670, globals=0x19f5580, 
    locals=0x0, args=0x683b00, argcount=0, kws=0x683b00, kwcount=2, 
    defs=0x1d2a1d8, defcount=1, closure=0x0) at Python/ceval.c:3253
#132 0x00007ffff7acab78 in fast_function (func=0x1d2c840, 
    pp_stack=0x7fffffffe450, n=4, na=0, nk=2) at Python/ceval.c:4117
#133 0x00007ffff7aca704 in call_function (pp_stack=0x7fffffffe450, oparg=512)
    at Python/ceval.c:4042
#134 0x00007ffff7ac4e9e in PyEval_EvalFrameEx (f=0x683970, throwflag=0)
    at Python/ceval.c:2666
#135 0x00007ffff7ac79ba in PyEval_EvalCodeEx (co=0x1185eb0, globals=0x6836d0, 
    locals=0x6836d0, args=0x0, argcount=0, kws=0x0, kwcount=0, defs=0x0, 
    defcount=0, closure=0x0) at Python/ceval.c:3253
#136 0x00007ffff7abcff8 in PyEval_EvalCode (co=0x1185eb0, globals=0x6836d0, 
    locals=0x6836d0) at Python/ceval.c:667
#137 0x00007ffff7afb1d6 in run_mod (mod=0x1237138, 
    filename=0x7fffffffed79 "test_period.py", globals=0x6836d0, 
    locals=0x6836d0, flags=0x7fffffffe9c0, arena=0x686f90)
    at Python/pythonrun.c:1353
#138 0x00007ffff7afb153 in PyRun_FileExFlags (fp=0x683940, 
    filename=0x7fffffffed79 "test_period.py", start=257, globals=0x6836d0, 
    locals=0x6836d0, closeit=1, flags=0x7fffffffe9c0)
    at Python/pythonrun.c:1339
---Type <return> to continue, or q <return> to quit---
#139 0x00007ffff7af98bb in PyRun_SimpleFileExFlags (fp=0x683940, 
    filename=0x7fffffffed79 "test_period.py", closeit=1, flags=0x7fffffffe9c0)
    at Python/pythonrun.c:943
#140 0x00007ffff7af8ec7 in PyRun_AnyFileExFlags (fp=0x683940, 
    filename=0x7fffffffed79 "test_period.py", closeit=1, flags=0x7fffffffe9c0)
    at Python/pythonrun.c:747
#141 0x00007ffff7b15234 in Py_Main (argc=2, argv=0x7fffffffeb48)
    at Modules/main.c:639
#142 0x0000000000400784 in main (argc=2, argv=0x7fffffffeb48)
    at ./Modules/python.c:23
```
