Polishing

- Use Java 8 idioms more consistently.
- Use newer Guava idioms more consistently.
- Apply some IntelliJ IDEA refactoring suggestions.
- Other changes made for readability and/or brevity.

Closes #3462.

PiperOrigin-RevId: 164700946

src/main/java/com/google/devtools/skylark/Skylark.java

diff --git a/src/main/java/com/google/devtools/skylark/Skylark.java b/src/main/java/com/google/devtools/skylark/Skylark.java
index 9f1181e..3e4d77e 100644
--- a/src/main/java/com/google/devtools/skylark/Skylark.java
+++ b/src/main/java/com/google/devtools/skylark/Skylark.java
@@ -105,7 +105,7 @@
       System.err.println(e.print());
       return 1;
     } catch (Exception e) {
-      System.err.println(e);
+      e.printStackTrace(System.err);
       return 1;
     }
   }