anaconda下打開Spyder報錯AttributeError: '_ModuleMock' object has no attribute 'PLUGIN_CLASS'

詳細報錯爲

plugin = mod.PLUGIN_CLASS(self)
AttributeError: '_ModuleMock' object has no attribute 'PLUGIN_CLASS'

Version and main components
Spyder Version: 3.2.3
Python Version: 3.6.2
Qt Versions: 5.6.2, PyQt5 5.6 on Windows

Dependencies
pyflakes >=0.6.0 :  1.6.0 (OK)
pycodestyle >=2.3:  2.3.1 (OK)
pygments >=2.0   :  2.2.0 (OK)
pandas >=0.13.1  :  0.20.3 (OK)
numpy >=1.7      :  1.13.3 (OK)
sphinx >=0.6.6   :  1.6.3 (OK)
rope >=0.9.4     :  0.9.4-1 (OK)
jedi >=0.9.0     :  0.10.2 (OK)
nbconvert >=4.0  :  5.2.1 (OK)
sympy >=0.7.3    :  1.1.1 (OK)
cython >=0.21    :  0.26 (OK)
qtconsole >=4.2.0:  4.3.1 (OK)
IPython >=4.0    :  6.1.0 (OK)
pylint >=0.25    :  1.7.2 (OK)

而這個問題在版本3.3.1中已解決，在anaconda Prompt中輸入

conda install spyder=3.3.1

而輸入conda update spyder無法更新，不知道爲什麼…