Configuration locations for Spring do not allow missing for file URLs

[jgibson]

When the spring configuration location is specified as a file: URL if it isn't found then it causes an error. classpath: URLs fail gracefully because Spring's ResourceUtils.getURL() throws a FileNotFoundException when the classpath URL can't be resolved. In contrast File URLs only cause that exception when they are invalid as both a URL and as a filepath (something that I was unable to do on a Mac running Java 8, perhaps windows is different).

File URLs should fail gracefully to allow the multiple configuration logic to behave properly, just like they do for classpath URLs.

Caused by: ch.qos.logback.core.joran.spi.JoranException: Could not open URL [file:/Users/foo/bar/logback.xml].
       at ch.qos.logback.core.joran.GenericConfigurator.doConfigure(GenericConfigurator.java:53)
       at ch.qos.logback.classic.util.ContextInitializer.configureByResource(ContextInitializer.java:75)
       at ch.qos.logback.ext.spring.LogbackConfigurer.initLogging(Unknown Source)
       ... 94 more
Caused by: java.io.FileNotFoundException: /Users/foo/bar/logback.xml (No such file or directory)
       at java.io.FileInputStream.open0(Native Method)
       at java.io.FileInputStream.open(FileInputStream.java:195)
       at java.io.FileInputStream.<init>(FileInputStream.java:138)
       at java.io.FileInputStream.<init>(FileInputStream.java:93)
       at sun.net.www.protocol.file.FileURLConnection.connect(FileURLConnection.java:90)
       at sun.net.www.protocol.file.FileURLConnection.getInputStream(FileURLConnection.java:188)
       at ch.qos.logback.core.joran.GenericConfigurator.doConfigure(GenericConfigurator.java:48)
       ... 96 more