Throw EmbeddedContainerExceptions from Tomcat

Wrap Tomcat start errors in EmbeddedContainerException.

Fixes gh-4204

spring-boot/src/main/java/org/springframework/boot/context/embedded/tomcat/TomcatEmbeddedServletContainer.java

@@ -146,6 +146,7 @@ public class TomcatEmbeddedServletContainer implements EmbeddedServletContainer
 
 	@Override
 	public void start() throws EmbeddedServletContainerException {
+		try {
 			addPreviouslyRemovedConnectors();
 			Connector connector = this.tomcat.getConnector();
 			if (connector != null && this.autoStart) {
@@ -159,6 +160,11 @@ public class TomcatEmbeddedServletContainer implements EmbeddedServletContainer
 			TomcatEmbeddedServletContainer.logger
 					.info("Tomcat started on port(s): " + getPortsDescription(true));
 		}
+		catch (Exception ex) {
+			throw new EmbeddedServletContainerException(
+					"Unable to start embedded Tomcat servlet container", ex);
+		}
+	}
 
 	private boolean connectorsHaveFailedToStart() {
 		for (Connector connector : this.tomcat.getService().findConnectors()) {

spring-boot/src/test/java/org/springframework/boot/context/embedded/tomcat/TomcatEmbeddedServletContainerFactoryTests.java

@@ -41,6 +41,7 @@ import org.apache.coyote.http11.AbstractHttp11JsseProtocol;
 import org.junit.Test;
 import org.mockito.InOrder;
 import org.springframework.boot.context.embedded.AbstractEmbeddedServletContainerFactoryTests;
+import org.springframework.boot.context.embedded.EmbeddedServletContainerException;
 import org.springframework.boot.context.embedded.Ssl;
 import org.springframework.util.SocketUtils;
 
@@ -278,7 +279,7 @@ public class TomcatEmbeddedServletContainerFactoryTests
 					TomcatEmbeddedServletContainerFactoryTests.this.container.start();
 					fail();
 				}
-				catch (IllegalStateException ex) {
+				catch (EmbeddedServletContainerException ex) {
 					// Ignore
 				}
 			}
@@ -308,7 +309,7 @@ public class TomcatEmbeddedServletContainerFactoryTests
 					TomcatEmbeddedServletContainerFactoryTests.this.container.start();
 					fail();
 				}
-				catch (IllegalStateException ex) {
+				catch (EmbeddedServletContainerException ex) {
 					// Ignore
 				}
 			}
@@ -382,7 +383,6 @@ public class TomcatEmbeddedServletContainerFactoryTests
 	private void doWithBlockedPort(final int port, Runnable action) throws IOException {
 		ServerSocket serverSocket = new ServerSocket();
 		serverSocket.bind(new InetSocketAddress(port));
-
 		try {
 			action.run();
 		}