I had to rebuild the undercloud for you. :)

[stack@tripleo ~]$ cat /etc/redhat-release 
CentOS Linux release 7.6.1810 (Core)

[stack@tripleo ~]$ openstack
/usr/lib/python2.7/site-packages/requests/__init__.py:91: RequestsDependencyWarning: urllib3 (1.24.1) or chardet (2.2.1) doesn't match a supported version!
  RequestsDependencyWarning)
(openstack) exit

[stack@tripleo ~]$ sudo yum install --assumeyes python2-chardet 
Loaded plugins: fastestmirror, priorities
Loading mirror speeds from cached hostfile
 * base: mirror.genesisadaptive.com
 * extras: mirror.genesisadaptive.com
 * updates: mirror.genesisadaptive.com
2 packages excluded due to repository priority protections
Resolving Dependencies
--> Running transaction check
---> Package python-chardet.noarch 0:2.2.1-1.el7_1 will be obsoleted
---> Package python2-chardet.noarch 0:3.0.4-7.el7 will be obsoleting
--> Finished Dependency Resolution

Dependencies Resolved

========================================================================================================================================================================================================
 Package                                          Arch                                    Version                                         Repository                                               Size
========================================================================================================================================================================================================
Installing:
 python2-chardet                                  noarch                                  3.0.4-7.el7                                     delorean-stein-testing                                  185 k
     replacing  python-chardet.noarch 2.2.1-1.el7_1

Transaction Summary
========================================================================================================================================================================================================
Install  1 Package

Total download size: 185 k
Downloading packages:
python2-chardet-3.0.4-7.el7.noarch.rpm                                                                                                                                           | 185 kB  00:00:00     
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
  Installing : python2-chardet-3.0.4-7.el7.noarch                                                                                                                                                   1/2 
  Erasing    : python-chardet-2.2.1-1.el7_1.noarch                                                                                                                                                  2/2 
  Verifying  : python2-chardet-3.0.4-7.el7.noarch                                                                                                                                                   1/2 
  Verifying  : python-chardet-2.2.1-1.el7_1.noarch                                                                                                                                                  2/2 

Installed:
  python2-chardet.noarch 0:3.0.4-7.el7                                                                                                                                                                  

Replaced:
  python-chardet.noarch 0:2.2.1-1.el7_1                                                                                                                                                                 

Complete!

[stack@tripleo ~]$ openstack
(openstack)