Fix startup logic for old Postgres versions

Closes rust-postgres#167

Author: sfackler

src/lib.rs

@@ -471,6 +471,8 @@ impl InnerConnection {
                                 ORDER BY enumsortorder") {
             Ok(..) => {}
             Err(Error::Io(e)) => return Err(ConnectError::Io(e)),
+            // Old versions of Postgres and things like Redshift don't support enums
+            Err(Error::Db(ref e)) if e.code == SqlState::UndefinedTable => {}
             Err(Error::Db(e)) => return Err(ConnectError::Db(e)),
             Err(Error::Conversion(_)) => unreachable!(),
         }
@@ -484,6 +486,8 @@ impl InnerConnection {
                                 ORDER BY attnum") {
             Ok(..) => {}
             Err(Error::Io(e)) => return Err(ConnectError::Io(e)),
+            // Old versions of Postgres and things like Redshift don't support composites
+            Err(Error::Db(ref e)) if e.code == SqlState::UndefinedTable => {}
             Err(Error::Db(e)) => return Err(ConnectError::Db(e)),
             Err(Error::Conversion(_)) => unreachable!(),
         }