endless error loop

This occurring with:

PyCharm 2017.2.3

Build #PY-172.3968.37, built on September 1, 2017
Licensed to Oracle

JRE: 1.8.0_152-release-915-b11 x86_64
JVM: OpenJDK 64-Bit Server VM by JetBrains s.r.o
Mac OS X 10.12.6

I am not importing matplotlib, yet executing an endless barrage of errors -- repeated endlessly -- when I execute commands in the console:

KeyError: 'matplotlib.pyplot'
Traceback (most recent call last):
File "/Applications/PyCharm.app/Contents/helpers/pydev/pydevconsole.py", line 207, in process_exec_queue
inputhook()
File "/Applications/PyCharm.app/Contents/helpers/pydev/pydev_ipython/inputhook.py", line 428, in inputhook_mac
pyplot = sys.modules['matplotlib.pyplot']