Description of problem:
Yesterday an update to EL7 EPEL brought in Python 3.6. The automatic update switches the default symlink from python34 to python36. 

However, the update did not pick up all additional Python dependencies, like in our case python34-PyYAML was not updated so all scripts using "import yaml" started failing because the system was executing /usr/bin/python3 with the new python3.6, but the installed python3-PyYAML package was only present for python3.4. 

Manually installing python36-PyYAML is required as a workaround, but a general system update should not be breaking the internal dependencies. 

Version-Release number of selected component (if applicable):
python34-* auto updated to python36-*

How reproducible:
always

Steps to Reproduce:
1. run centos 7 with epel enabled and with the older python3 (that's python 3.4 installed)
2. create a script with #!/usr/bin/python3 or env python3, and add "import yaml" to the script. 
3. For yaml support install python34-PyYAML
4. Run yum update, and try to run the script

Actual results:

Script starts failing with missing yaml module

Expected results:
python update to 3.6 should also install other python modules that exist in the system and pertain to the already installed minor version, so when python 3.4 is updated to 3.6, PyYAML3.6 should be installed if PyYAML3.4 already is in the system. 

Additional info: