Trying to execute LibcxxOnOlderSytems (2nd ed.)

[ftp83plus]

Hello there, 

***
Please excuse me for double-post if so, I never got any confirmation this message was received, even though this mailing list is very active.
***

I am trying to execute the instructions on this page https://trac.macports.org/wiki/LibcxxOnOlderSystems, but am stuck at step 4 of Bootstrapping 3:
On instruction 
sudo port -v uninstall llvm-3.4 clang-3.4
I get 

Warning: Failed to execute portfile from registry for llvm-3.4 @3.4.2_8
--->  Unable to uninstall llvm-3.4 @3.4.2_8, the following ports depend on it:
--->  	cctools @877.5_1+llvm34
--->  	ld64-136 @136_2+llvm34

Not sure I understand the logic fault here…

P