Updating non-MSL packages can install the wrong version

[jborbely]

msl-io depends on xlrd<2.0; however, executing

msl update --non-msl

could install the wrong version of xlrd, for example,

The following non-MSL packages will be UPDATED:

    xlrd             1.2.0  --> 2.0.1,<2.0  [PyPI]

msl-package-manager will discover inconsistent dependencies when a package is updated (via pip's logging of error messages to the console) but this dependency resolver of pip was officially added in version 20.3. Therefore, as long as pip v20.3+ is installed the appropriate version of xlrd would get installed, but the latest version would be initially installed. For older versions of pip that do not write error messages for inconsistent dependencies to the console, the wrong version of xlrd would remain installed.

[jborbely]

fixed in 8d4ab5b