Fix get_pg_version for linux mint

issue #100

Author: vshepard

testgres/utils.py

@@ -177,16 +177,17 @@ def get_pg_version(bin_dir=None):
     Return PostgreSQL version provided by postmaster.
     """
 
-    # get raw version (e.g. postgres (PostgreSQL) 9.5.7)
+    # Get raw version (e.g. postgres (PostgreSQL) 9.5.7)
     postgres_path = os.path.join(bin_dir, 'postgres') if bin_dir else get_bin_path('postgres')
     _params = [postgres_path, '--version']
     raw_ver = tconf.os_ops.exec_command(_params, encoding='utf-8')
 
-    # Remove "(Homebrew)" if present
+    # Remove "(Homebrew)" and "(Ubuntu <version>)" if present
     raw_ver = raw_ver.replace('(Homebrew)', '').strip()
+    raw_ver = re.sub(r'\(Ubuntu[^)]*\)', '', raw_ver).strip()
 
-    # cook version of PostgreSQL
-    version = raw_ver.strip().split(' ')[-1] \
+    # Cook version of PostgreSQL
+    version = raw_ver.split(' ')[-1] \
                      .partition('devel')[0] \
                      .partition('beta')[0] \
                      .partition('rc')[0]