include filename/path details in exception messages

Author: dlenski

zxing/__init__.py

@@ -45,22 +45,22 @@ def decode(self, filename, try_harder=False, possible_formats=None):
         try:
             p = sp.Popen(cmd, stdout=sp.PIPE, stderr=sp.STDOUT, universal_newlines=False)
         except FileNotFoundError as e:
-            raise BarCodeReaderException("Java binary specified does not exist", self.java, e)
+            raise BarCodeReaderException("Java binary specified (%s) does not exist" % self.java, self.java, e)
         except PermissionError as e:
-            raise BarCodeReaderException("Java binary specified is not executable", self.java, e)
-        stdout, _ = p.communicate()
+            raise BarCodeReaderException("Java binary specified (%s) is not executable" % self.java, self.java, e)
+        stdout, stderr = p.communicate()
 
         if stdout.startswith((b'Error: Could not find or load main class com.google.zxing.client.j2se.CommandLineRunner',
                               b'Exception in thread "main" java.lang.NoClassDefFoundError:')):
-            raise BarCodeReaderException("Java JARs not found in expected directory", self.classpath)
+            raise BarCodeReaderException("Java JARs not found in classpath (%s)" % self.classpath, self.classpath)
         elif stdout.startswith(b'''Exception in thread "main" javax.imageio.IIOException: Can't get input stream from URL!'''):
-            raise BarCodeReaderException("Could not find image path", filename)
+            raise BarCodeReaderException("Could not find image path: %s" % filename, filename)
         elif stdout.startswith(b'''Exception in thread "main" java.io.IOException: Could not load '''):
             raise BarCodeReaderException("Java library could not read image; is it in a supported format?", filename)
         elif stdout.startswith(b'''Exception '''):
             raise BarCodeReaderException("Unknown Java exception: %s" % stdout)
         elif p.returncode:
-            raise BarCodeReaderException("Unexpected subprocess return code %d" % p.returncode, self.java)
+            raise BarCodeReaderException("Unexpected Java subprocess return code %d" % p.returncode, self.java)
 
         return BarCode.parse(stdout)