[MacPorts] #31702: port select fails if symlink already exists from earlier installation

[MacPorts]

#31702: port select fails if symlink already exists from earlier installation
---------------------------+--------------------------------
  Reporter:  gunnlaugur@…  |      Owner:  macports-tickets@…
      Type:  defect        |     Status:  new
  Priority:  Normal        |  Milestone:
 Component:  base          |    Version:  2.0.3
Resolution:                |   Keywords:
      Port:                |
---------------------------+--------------------------------

Comment (by akim.demaille@…):

 I have migrated from Python 3.4 to Python 3.5, but although there is no
 longer pip-3.4 installed on my machine:

 {{{
 $ port installed | grep pip
   pip_select @0.1_0 (active)
   py35-pip @8.1.1_0 (active)
 }}}

 there is still a symlink installed:

 {{{
 $ ls -l /opt/local/etc/select/pip/current
 lrwxr-xr-x  1 root  admin  5  6 mar  2015
 /opt/local/etc/select/pip/current -> pip34
 }}}

 that select does not seem to see:

 {{{
 $ sudo port select --summary
 Name       Selected      Options
 ====       ========      =======
 autopep8   none          autopep8-34 none
 awscli     none          py34-awscli none
 clang      none          mp-clang-3.4 mp-clang-3.5 mp-clang-3.6 mp-
 clang-3.7 mp-clang-3.8 none
 cython     none          cython27 cython34 none
 gcc        none          mp-gcc49 mp-gcc5 mp-gcc6 none
 ipython    none          py34-ipython py35-ipython none
 ipython3   py35-ipython  py34-ipython py35-ipython none
 llvm       none          mp-llvm-3.4 mp-llvm-3.5 mp-llvm-3.6 mp-llvm-3.7
 mp-llvm-3.8 none
 nosetests  none          nosetests27 nosetests34 none
 pep8       none          pep8-34 none
 pip        none          pip35 none
 python     python35      python26-apple python27 python27-apple python34
 python35 none
 python2    none          python27 none
 python3    python34      python34 python35 none
 sphinx     py34-sphinx   py34-sphinx none
 wxWidgets  none          wxWidgets-3.0 none
 }}}

 so it fails to upgrade my selection:

 {{{
 $ sudo port select --set pip pip35
 Selecting 'pip35' for 'pip' failed: symlink:
 /opt/local/etc/select/pip/current -> pip35: file already exists
 }}}

 Sure, I could do that by hand, but I shouldn't have to do that.

-- 
Ticket URL: <https://trac.macports.org/ticket/31702#comment:4>
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