Unintentionally finding two different files with the same python interpreter and system path

Question

I'm trying to run the Spyder IDE but it fails because it imports the wrong file. I get an ImportError attempting to run it from the command line:

$ /opt/anaconda3/bin/spyder 
Traceback (most recent call last):
  File "/opt/anaconda3/bin/spyder", line 6, in <module>
    sys.exit(spyder.app.start.main())
  File "/opt/anaconda3/lib/python3.5/site-packages/spyder/app/start.py", 
line 103, in main
    from spyder.app import mainwindow
  File "/opt/anaconda3/lib/python3.5/site-packages/spyder/app/mainwindow.py",
 line 78, in <module>
    from qtpy.compat import from_qvariant
  File "/opt/anaconda3/lib/python3.5/site-packages/qtpy/compat.py", 
line 15, in <module>
    from qtpy.QtWidgets import QFileDialog
  File "/opt/anaconda3/lib/python3.5/site-packages/qtpy/QtWidgets.py", 
line 27, in <module>
    from PyQt5.QtWidgets import *
ImportError: /opt/anaconda3/lib/python3.5/site-packages/PyQt5/Qt/lib/libQt5Gui.so.5:
symbol _Z10qAllocMoreii, version Qt_5 not defined in file libQt5Core.so.5 with 
link time reference

However, when I run from the python interpreter at /opt/anaconda3/bin/python the command from PyQt5.QtWidgets import *, it works fine. Ok, so naturally I think this is a sys.path issue. So I modify /opt/anaconda3/lib/python3.5/site-packages/qtpy/QtWidgets.py to print out the system path and system executable. The relevant segment of code is:

print(sys.path)
print(sys.executable)
from PyQt5.QtWidgets import *

Which prints the result:

['/opt/anaconda3/bin', '/opt/anaconda3/lib/python35.zip', 
'/opt/anaconda3/lib/python3.5', 
'/opt/anaconda3/lib/python3.5/plat-linux', 
'/opt/anaconda3/lib/python3.5/lib-dynload', 
'/opt/anaconda3/lib/python3.5/site-packages', 
'/opt/anaconda3/lib/python3.5/site-packages/Sphinx-1.4.6-py3.5.egg', 
'/opt/anaconda3/lib/python3.5/site-packages/setuptools-27.2.0-py3.5.egg']

/opt/anaconda3/bin/python

The result from the interpreter for the same two commands is:

['', '/opt/anaconda3/lib/python35.zip', 
'/opt/anaconda3/lib/python3.5', 
'/opt/anaconda3/lib/python3.5/plat-linux', 
'/opt/anaconda3/lib/python3.5/lib-dynload', 
'/opt/anaconda3/lib/python3.5/site-packages', 
'/opt/anaconda3/lib/python3.5/site-packages/Sphinx-1.4.6-py3.5.egg', 
'/opt/anaconda3/lib/python3.5/site-packages/setuptools-27.2.0-py3.5.egg']

/opt/anaconda3/bin/python

So the paths are exactly the same except for the first directory, but that is irrelevant because the interpreter finds the appropriate library in the right directory:

$ /opt/anaconda3/bin/python
>>> import PyQt5.QtWidgets
>>> print(PyQt5.QtWidgets)
<module 'PyQt5.QtWidgets' from 
'/opt/anaconda3/lib/python3.5/site-packages/PyQt5/QtWidgets.so'>

So in summary, even though I'm using the same interpreter with the same system path, I find two different files in two different locations with the same import command. How is that possible? How do I prevent it doing whatever it is doing?