Extract function
Format error message for easier readability

```
Bad Markdown URL in service-manual/agile/features-of-agile.md:
extra closing bracket at line 30, column 27
Bad Markdown URL in service-manual/agile/features-of-agile.md:
extra closing bracket at line 32, column 19
```

compared with

```
Bad Markdown URL in service-manual/agile/features-of-agile.md:
	extra closing bracket at line 30, column 27
Bad Markdown URL in service-manual/agile/features-of-agile.md:
	extra closing bracket at line 32, column 19
```