Try to sort search paths by psql version

Previously the search paths for the psql binaries was not sorted. So
multiples postgresql versions on the same system may be used (usually the
older one was choosen first)

Try to return the paths sorted by postgresql version (most recent first)
for each glob search path

src/testing/postgresql.py

@@ -19,18 +19,36 @@
 import subprocess
 from glob import glob
 from contextlib import closing
+from distutils.version import LooseVersion
 
 from testing.common.database import (
     Database, DatabaseFactory, get_path_of, SkipIfNotInstalledDecorator
 )
 
-
 __all__ = ['Postgresql', 'skipIfNotFound']
 
+
+def sorted_paths(glob_pattern):
+    """
+    Try to return search paths sorted by version number
+    (latest version first)
+
+    """
+    values = glob(glob_pattern)
+    try:
+        idx = glob_pattern.index('*')
+
+        # -> [('9.4', '/usr/lib/postgresql/9.4')]
+        matches = [(LooseVersion(match[idx:]), match) for match in values]
+
+        return [path for _, path in sorted(matches, reverse=True)]
+    except Exception:
+        return values
+
 SEARCH_PATHS = (['/usr/local/pgsql', '/usr/local'] +
-                glob('/usr/pgsql-*') +  # for CentOS/RHEL
-                glob('/usr/lib/postgresql/*') +  # for Debian/Ubuntu
-                glob('/opt/local/lib/postgresql*'))  # for MacPorts
+                sorted_paths('/usr/pgsql-*') +  # for CentOS/RHEL
+                sorted_paths('/usr/lib/postgresql/*') +  # for Debian/Ubuntu
+                sorted_paths('/opt/local/lib/postgresql*'))  # for MacPorts
 
 
 class Postgresql(Database):