## What changes were proposed in this pull request?
This issue fixes the error message indentation consistently with other set queries (EXCEPT/INTERSECT).
**Before (4 lines)**
```
scala> sql("(select 1) union (select 1, 2)").head
org.apache.spark.sql.AnalysisException:
Unions can only be performed on tables with the same number of columns,
but one table has '2' columns and another table has
'1' columns;
```
**After (one-line)**
```
scala> sql("(select 1) union (select 1, 2)").head
org.apache.spark.sql.AnalysisException: Unions can only be performed on tables with the same number of columns, but one table has '2' columns and another table has '1' columns;
```
**Reference (EXCEPT / INTERSECT)**
```
scala> sql("(select 1) intersect (select 1, 2)").head
org.apache.spark.sql.AnalysisException: Intersect can only be performed on tables with the same number of columns, but the left table has 1 columns and the right has 2;
```
## How was this patch tested?
Manual.
Author: Dongjoon Hyun <dongjoon@apache.org>
Closes#13043 from dongjoon-hyun/SPARK-15265.
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