Macports problems after upgrading to Yosemite

[Chris Freyberg]

I recently upgraded to Yosemite.

I use macports very infrequently and with considerable trepidation 
because many of the messages it spits out don't mean a lot to me. Prior 
to the upgrade to Yosemite, I think I had two ports installed.
Today I wanted to install a new port, nco.

After some initial difficulties, I followed the migration process 
(https://trac.macports.org/wiki/Migration) WITH THE exception of 
checking the macports.conf file, which I could not locate.

Now I am having lots of pretty persistent problems with messages like:-

"Activating antlr @2.7.7_1
Error: org.macports.activate for port antlr returned: Image error: 
/opt/local/bin/antlr already exists and does not belong to a registered 
port.  Unable to activate port antlr. Use 'port -f activate antlr' to 
force the activation.
Error: Failed to install antlr"

I went on for a while trying to install all the dependencies of nco by 
liberally applying the -f option, with some success, until I realised 
there was the following disjointed sequence of events:- antlr @2.7.7_1 
is installed and activated, then later macports tries to do it again (as 
it is a dependency).

"
{ reinstall at end of migration}
$  sudo ./restore_ports.tcl myports.txt
Password:
--->  Fetching archive for antlr
--->  Attempting to fetch antlr-2.7.7_1.darwin_14.x86_64.tbz2 from 
http://packages.macports.org/antlr
--->  Attempting to fetch antlr-2.7.7_1.darwin_14.x86_64.tbz2 from 
http://lil.fr.packages.macports.org/antlr
--->  Attempting to fetch antlr-2.7.7_1.darwin_14.x86_64.tbz2 from 
http://mse.uk.packages.macports.org/sites/packages.macports.org/antlr
--->  Fetching distfiles for antlr
--->  Verifying checksums for antlr
--->  Extracting antlr
--->  Applying patches to antlr
--->  Configuring antlr
--->  Building antlr
--->  Staging antlr into destroot
--->  Installing antlr @2.7.7_1
--->  Cleaning antlr
.
.
.
{ reinstall completes, seemingly without problems}
.
.
.
{ a few minutes later }
$ sudo port install nco
--->  Computing dependencies for nco
--->  Dependencies to be installed: antlr bison texinfo perl5.16 gdbm 
udunits2 autoconf perl5 automake libtool wget gnutls gmp libtasn1 nettle 
p11-kit desktop-file-utils glib2 libffi popt libxslt pcre bzip2 libedit
--->  Activating antlr @2.7.7_1
Error: org.macports.activate for port antlr returned: Image error: 
/opt/local/bin/antlr already exists and does not belong to a registered 
port.  Unable to activate port antlr. Use 'port -f activate antlr' to 
force the activation.
Error: Failed to install antlr
"

To me, this indicates that macports has got amnesia. Even though it 
claims to have installed antlr xxx cleanly, it first of all doesn't 
think it has (because it now needs to install it), but it finds the 
download, verification and configuration already done so it tries to 
activate and falls over. So may be the earlier install, at the end of 
migration, did not get registered?

Any ideas as to how I might deal with this, please.

Thanks
Chris F