Description of problem:
IIUIC, Collate and Ctype settings of database objects (tables at least) when creating are taken from current $LANG environment variable if not specified explicitly using --lc-collate when running initdb. So, when I initialize postgresql database cluster with $LANG set to en_US.UTF-8 (defined so in /etc/locale.conf), the tables will look like the following:

postgres=# \list
                                  List of databases
   Name    |  Owner   | Encoding |   Collate   |    Ctype    |   Access privileges   
-----------+----------+----------+-------------+-------------+-----------------------
 postgres  | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | 
 template0 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres          +
           |          |          |             |             | postgres=CTc/postgres
 template1 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres          +
           |          |          |             |             | postgres=CTc/postgres

Then, when I change /etc/locale.conf to a different value (actually I don't remember I done it consciously, but it had to be changed by someone/something probably), say en_US.utf8, the next postgresql upgrade fails because it checks the collations to be the same with the following error message:

lc_collate cluster values do not match:  old "en_US.UTF-8", new "en_US.utf8"

That's because a new cluster is initialized in one step during upgrading process and thus the new collation is used (the one set in /etc/locale.conf).

Version-Release number of selected component (if applicable):
postgresql-server-9.3.0-1.fc20.x86_64

How reproducible:
every-time

Steps to Reproduce:
1. start with postgresql-9.2.x
2. # systemctl stop postgresql
3. # mv /var/lib/pgsql/{data,backup-data}
4. set LANG=en_US.UTF-8 in /etc/locale.conf
5. # postgresql-setup initdb
6. upgrade to postgresql-9.3.x
7. Change LANG=en_US.utf8 in /etc/locale.conf
9. # postgresql-setup upgrade

Actual results:
upgrade fails, /var/lib/pgsql/pgupgrade.log includes:
lc_collate cluster values do not match:  old "en_US.UTF-8", new "en_US.utf8"

Expected results:
upgrade succeeds

Additional info:
IMHO, the only thing postgresql can do better about that is to explicitly define the same collation in initdb call (called in postgresql-setup script) as the former data stack had (automatically or offer a way to define it by hand), since this is required in the 5th step of pg_upgrade in [1]:

"Initialize the new PostgreSQL cluster
Initialize the new cluster using initdb. Again, use compatible initdb flags that match the old cluster. Many prebuilt installers do this step automatically. There is no need to start the new cluster."

Anyway, even if this is not done by postgresql automatically, this problem during upgrading can be quite easily fixed by changing /etc/locale.conf value to match older collate settings for the time of upgrading.

[1] http://www.postgresql.org/docs/9.3/static/pgupgrade.html