Handle build compilation failures better.

src/main/kotlin/com/beust/kobalt/Main.kt

@@ -11,6 +11,7 @@ import com.beust.kobalt.kotlin.BuildFile
 import com.beust.kobalt.kotlin.BuildFileCompiler
 import com.beust.kobalt.maven.DepFactory
 import com.beust.kobalt.maven.Http
+import com.beust.kobalt.maven.KobaltException
 import com.beust.kobalt.maven.LocalRepo
 import com.beust.kobalt.misc.*
 import com.beust.kobalt.wrapper.Wrapper
@@ -94,6 +95,9 @@ private class Main @Inject constructor(
 //            runTest()
             try {
                 result = runWithArgs(jc, args)
+            } catch(ex: KobaltException) {
+                error(ex.message ?: "", ex)
+                result = 1
             } finally {
                 executors.shutdown()
             }

src/main/kotlin/com/beust/kobalt/kotlin/BuildFileCompiler.kt

@@ -96,12 +96,17 @@ public class BuildFileCompiler @Inject constructor(@Assisted("buildFiles") val b
         } else {
             log(2, "Need to recompile ${buildFile.name}")
 
+            buildScriptJarFile.delete()
             kotlinCompilePrivate {
                 classpath(files.kobaltJar)
                 classpath(pluginUrls.map { it.file })
                 sourceFiles(listOf(buildFile.path.toFile().absolutePath))
                 output = buildScriptJarFile
             }.compile(context = context)
+
+            if (! buildScriptJarFile.exists()) {
+                throw KobaltException("Could not compile ${buildFile.name}")
+            }
         }
     }
 

src/main/kotlin/com/beust/kobalt/misc/KobaltLogger.kt

@@ -49,11 +49,12 @@ class Logger(val dev: Boolean) {
 
     final fun error(tag: String, message: String, e: Throwable? = null) {
         println(getPattern("***** E", "***** ERROR ", tag, message) +
-                if (e != null) " Exception: " + e.message else "")
-        e?.printStackTrace()
+                if (e != null && KobaltLogger.LOG_LEVEL > 1) " Exception: " + e.message else "")
+        if (KobaltLogger.LOG_LEVEL > 1) {
+            e?.printStackTrace()
+        }
     }
 
-
     final fun warn(tag: String, message: String, e: Throwable? = null) =
         println(getPattern("W", "***** WARNING ${e?.message}", tag, message))