除非先导入pyplot，否则Scipy.signal不会导入

这太奇怪了这在每次导入时都以两种不同的方式失败

>>> import scipy.signal Traceback (most recent call last): File "<pyshell#0>", line 1, in <module> import scipy.signal File "C:\Users\ewwieser\AppData\Local\Programs\Python\Python35\lib\site-packages\scipy\signal\__init__.py", line 282, in <module> from .bsplines import * File "C:\Users\ewwieser\AppData\Local\Programs\Python\Python35\lib\site-packages\scipy\signal\bsplines.py", line 12, in <module> from scipy.special import comb, gamma File "C:\Users\ewwieser\AppData\Local\Programs\Python\Python35\lib\site-packages\scipy\special\__init__.py", line 627, in <module> from ._ufuncs import * File "scipy\special\_ufuncs.pyx", line 1, in init scipy.special._ufuncs (scipy\special\_ufuncs.c:26242) ImportError: DLL load failed: The specified module could not be found. >>> import matplotlib.pyplot >>> import scipy.signal Traceback (most recent call last): File "<pyshell#7>", line 1, in <module> import scipy.signal File "C:\Users\ewwieser\AppData\Local\Programs\Python\Python35\lib\site-packages\scipy\signal\__init__.py", line 282, in <module> from .bsplines import * File "C:\Users\ewwieser\AppData\Local\Programs\Python\Python35\lib\site-packages\scipy\signal\bsplines.py", line 12, in <module> from scipy.special import comb, gamma File "C:\Users\ewwieser\AppData\Local\Programs\Python\Python35\lib\site-packages\scipy\special\__init__.py", line 629, in <module> from .basic import * File "C:\Users\ewwieser\AppData\Local\Programs\Python\Python35\lib\site-packages\scipy\special\basic.py", line 14, in <module> from ._ufuncs import (ellipkm1, mathieu_a, mathieu_b, iv, jv, gamma, psi, zeta, ImportError: cannot import name 'ellipkm1'

而这工作得很好（在一个新鲜的shell）：

 >>> import matplotlib.pyplot >>> import scipy.signal >>>

我的设置是：

在Windows上的Python 3.5.1 x64
Numpy 1.11.0（从~gohlke安装）
Scipy 0.17.1（从~gohlke安装）
Matplotlib 1.5.1（直接pip install matplotlib ）

为什么import依赖于对方？这怎么可能呢？