pg9.4b1: unhelpful error message when creating a collation

sh> lsb_release -d  Description: Ubuntu 14.04 LTS  Codename: trusty
  sh> uname -a  Linux sto 3.13.0-24-generic #47-Ubuntu SMP Fri May 2 23:30:00 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
  sh> locale -a  C  C.UTF-8  en_AG  en_AG.utf8  en_AU.utf8  en_BW.utf8  en_CA.utf8  en_DK.utf8  en_GB.utf8  en_HK.utf8
en_IE.utf8 en_IN  en_IN.utf8  en_NG  en_NG.utf8  en_NZ.utf8  en_PH.utf8  en_SG.utf8  en_US.utf8  en_ZA.utf8  en_ZM
en_ZM.utf8 en_ZW.utf8  fr_FR.utf8  POSIX
 

# with postgresql 9.4 installed from apt.postgresql.org.
  sql> SELECT VERSION();  PostgreSQL 9.4beta1 on x86_64-unknown-linux-gnu, compiled by gcc (Ubuntu 4.8.2-19ubuntu1)
4.8.2,64-bit
 
  sql> \dOS+  +- same list as above with "locale"
  sql> SHOW lc_messages;  en_US.UTF-8

# stuff which is working as expected:
  sql> CREATE COLLATION "test0" (locale='C');  CREATE COLLATION
  sql> CREATE COLLATION "test1" (locale='en_US.UTF-8');  CREATE COLLATION
  sql> CREATE COLLATION "test2" (locale='en_US.UTF8');  CREATE COLLATION
  sql> CREATE COLLATION "test3" (locale='Foo');  ERROR:  could not create locale "test3": No such file or directory
DETAIL: The operating system could not find any locale data for the locale name "Foo".
 

# stuff which is incoherent:
  sql> CREATE COLLATION "french" (locale='fr_FR.utf8');  ERROR:  could not create locale "fr_FR.utf8": Success

The collation creation fails, not sure why yet. However, the "error .. 
success" message is especially unhelpful.

Raising client_min_messages does not add more information.

I could not get the same error with 9.3.4.

-- 
Fabien.