Python 3.7.4 (default, Aug 13 2019, 20:35:49) 
[GCC 7.3.0] :: Anaconda, Inc. on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import matplotlib.pyplot as plt
>>> plt.waitforbuttonpress()
QTimer::singleShot: Timers cannot have negative timeouts
True
>>> ```

**Expected outcome**

no warning

**Matplotlib version**
<!--Please specify your platform and versions of the relevant libraries you are using:-->
  * Operating system: Linux
  * Matplotlib version: 3.1.1
  * Matplotlib backend (`print(matplotlib.get_backend())`):Qt5Agg
  * Python version: 3.7.4
  * Jupyter version (if applicable):
  * Other libraries: 

<!--Please tell us how you installed matplotlib and python e.g., from source, pip, conda-->
<!--If you installed from conda, please specify which channel you used if not the default-->