/usr/bin/svn exists on Catalina, but is non-functional

[kencu (Ken)]

the fetch subroutine in base for svn does a bin check for svn on Catalina, but the svn bin is non-functional.

It hands off to another svn if one exists, otherwise generates an error.

Probably simplest if all os versions just depend on MacPorts subversion.

[kencu (Ken)]

Catalina:

 % /usr/bin/svn
svn: error: Failed to locate 'svn'.
svn: error: The subversion command line tools are no longer provided by Xcode.

[ryandesign (Ryan Carsten Schmidt)]

See #60854.

[kencu (Ken)]

right. thanks!