Http connection in JavaTextFileSource inside an exception

[zkaoudi]

Currently, the code for reading files remotely through an Http call in the JavaTextFileSource is inside a catch (Exception e):

https://github.com/apache/incubator-wayang/blob/31b5a295186f3d6d9ac3e0a18b2adf15b2304cc4/wayang-platforms/wayang-java/src/main/java/org/apache/wayang/java/operators/JavaTextFileSource.java#L98

This is problematic because, if a user just passes the wrong path to a local file, the exception message they get a Java class cast error instead of a file-does-not-exist error.