Merge pull request diffblue#544 from diffblue/jd/feature/validate_config_files

Validate that we have a config file for prepare-scan

Author: smowton

driver/run.py

@@ -469,10 +469,14 @@ def __main():
             cmdline.run_scan = ''
 
     # If we have an entry for prepare_scan but it's an empty string, default.
-    if cmdline.prepare_scan is not None and not cmdline.prepare_scan:
-        default_path = '../src/java-class-info/default_config.json'
-        if os.path.isfile(default_path):
-            cmdline.prepare_scan = os.path.abspath(default_path)
+    if cmdline.prepare_scan == '':
+        default_config_path = '../src/java-class-info/default_config.json'
+        if os.path.isfile(default_config_path):
+            cmdline.prepare_scan = os.path.abspath(default_config_path)
+        else:
+            print("ERROR: No config file for entry point detection passed in via --prepare-scan"
+                  " and the default file can't be found at {0}.".format(default_config_path))
+            return
 
     if cmdline.name is None:
         cmdline.name = os.path.basename(cmdline.install_dir)