pkg-deptree tsort loops are cyclic dependencies?

[Keith Harbaugh <harbaugh@math.georgetown.edu>]

Running pkg-deptree on my potato system produced this error output,
as well as some standard output.

$ pkg-deptree > pkg-deptree.lst
External tsort invocation returned an error:
tsort: -: input contains a loop:

tsort: END


Is the detected "loop" an example of cyclic dependencies?

Keith