The error I got today was related to speedtest-cli:

florians-MacBook-Pro$ speedtest
Traceback (most recent call last):
  File "/opt/local/bin/speedtest", line 6, in <module>
    from pkg_resources import load_entry_point
ModuleNotFoundError: No module named 'pkg_resources'

The macports package speedtest-cli is a terminal port for the popular speedtest.net. The source is available here.

I truly do not know after which modification/upgrade I got this error because I do not use this utility often. But I got it, and I had to deal with it.
It turns out I was missing some needed python packages:

florians-MacBook-Pro:fmbpro florian$ sudo port -v install py36-pip  
--->  Computing dependencies for py36-pip..
The following dependencies will be installed:  py36-setuptools
Continue? [Y/n]: y
--->  Fetching archive for py36-setuptools
--->  py36-setuptools-38.5.1_0.darwin_17.noarch.tbz2 doesn't seem to exist in /opt/local/var/macports/incoming/verified
--->  Attempting to fetch py36-setuptools-38.5.1_0.darwin_17.noarch.tbz2 from https://packages.macports.org/py36-setuptools
--->  Installing py36-setuptools @38.5.1_0
--->  Activating py36-setuptools @38.5.1_0
--->  Cleaning py36-setuptools
--->  Removing work directory for py36-setuptools
--->  Fetching archive for py36-pip
--->  py36-pip-9.0.1_0.darwin_17.noarch.tbz2 doesn't seem to exist in /opt/local/var/macports/incoming/verified
--->  Attempting to fetch py36-pip-9.0.1_0.darwin_17.noarch.tbz2 from https://packages.macports.org/py36-pip
--->  Installing py36-pip @9.0.1_0
--->  Activating py36-pip @9.0.1_0
--->  Cleaning py36-pip
--->  Removing work directory for py36-pip
--->  Updating database of binaries
--->  Scanning binaries for linking errors
--->  No broken files found.                             
--->  Some of the ports you installed have notes:
  py36-pip has the following notes:
    To make the Python 3.6 version of pip the one that is run when you execute the commands without a version suffix, e.g. 'pip', run:
    
    port select --set pip pip36

Error gone:

florians-MacBook-Pro:fmbpro florian$ speedtest
Retrieving speedtest.net configuration...
Retrieving speedtest.net server list...
Testing download speed........................................
Download: 197.49 Mbits/s
Testing upload speed..................................................
Upload: 99.36 Mbits/s