Added pylint formatter (#1995)

Fixes: #1953

@charliermarsh thank you for the tips in the issue.

I'm not very familiar with Rust, so please excuse if my string formatting syntax is messy.

In terms of testing, I compared output of `flake8 --format=pylint ` and `cargo run --format=pylint` on the same code and the output syntax seems to check out.

ruff_cli/src/commands.rs

@@ -319,6 +319,9 @@ pub fn explain(rule: &Rule, format: SerializationFormat) -> Result<()> {
         SerializationFormat::Gitlab => {
             bail!("`--explain` does not support GitLab format")
         }
+        SerializationFormat::Pylint => {
+            bail!("`--explain` does not support pylint format")
+        }
     };
     Ok(())
 }

ruff_cli/src/printer.rs

@@ -285,7 +285,7 @@ impl<'a> Printer<'a> {
                 }
             }
             SerializationFormat::Gitlab => {
-                // Generate JSON with errors in GitLab CI format
+                // Generate JSON with violations in GitLab CI format
                 // https://docs.gitlab.com/ee/ci/testing/code_quality.html#implementing-a-custom-tool
                 writeln!(stdout,
                     "{}",
@@ -312,6 +312,20 @@ impl<'a> Printer<'a> {
                     )?
                 )?;
             }
+            SerializationFormat::Pylint => {
+                // Generate violations in Pylint format.
+                // See: https://flake8.pycqa.org/en/latest/internal/formatters.html#pylint-formatter
+                for message in &diagnostics.messages {
+                    let label = format!(
+                        "{}:{}: [{}] {}",
+                        relativize_path(Path::new(&message.filename)),
+                        message.location.row(),
+                        message.kind.rule().code(),
+                        message.kind.body(),
+                    );
+                    writeln!(stdout, "{label}")?;
+                }
+            }
         }
 
         stdout.flush()?;