improve message readout for OpConfigError

nb-api/src/main/java/io/nosqlbench/nb/api/errors/BasicError.java

@@ -9,4 +9,7 @@ public class BasicError extends RuntimeException {
     public BasicError(String exception) {
         super(exception);
     }
+    public BasicError(String exception, Throwable cause) {
+        super(exception,cause);
+    }
 }

nb-api/src/main/java/io/nosqlbench/nb/api/errors/OpConfigError.java

@@ -0,0 +1,62 @@
+package io.nosqlbench.nb.api.errors;
+
+/**
+ * OpConfigErrors are {@link BasicError}s which are known to occur when
+ * there is an invalid set of configuration details for an op. This can
+ * occur when the user-provided op template data (such as from YAML)
+ * is being inspected by a driver adapter to synthesize operations
+ * (or functions which know how to do so).
+ */
+public class OpConfigError extends ActivityInitError {
+    private final String configSource;
+
+    public OpConfigError(String error) {
+        this(error,null);
+    }
+
+    public OpConfigError(String error, String configSource) {
+        super(error);
+        this.configSource = configSource;
+    }
+
+
+    public OpConfigError(String error, String configSource, Throwable cause) {
+        super(error,cause);
+        this.configSource = configSource;
+    }
+
+    public String getCfgSrc() {
+        return configSource;
+    }
+
+    @Override
+    public String getMessage() {
+        StringBuilder sb = new StringBuilder("Error while configuring op from workload template:");
+
+        String cfgsrc = configSource;
+        if (cfgsrc==null) {
+            Throwable cause = getCause();
+            while (cause instanceof OpConfigError && cfgsrc==null) {
+                cfgsrc = ((OpConfigError) cause).getCfgSrc();
+                cause = cause.getCause();
+            }
+        }
+
+        if (cfgsrc!=null) {
+            sb.append("configsource:" + configSource);
+        }
+
+        if (getCause()!=null) {
+            StackTraceElement causeFrame = getCause().getStackTrace()[0];
+            sb.append("\n\t caused by ")
+                .append(getCause().getMessage())
+                .append("\n\t at (")
+                .append(causeFrame.getFileName())
+                .append(":")
+                .append(causeFrame.getLineNumber())
+                .append(")");
+        }
+
+        return sb.toString();
+    }
+}