Add formatter for copy_rai_into_ndarray exceptions

This formatter converts the exceptions from copy_rai_into_ndarray into a
more human readable format.

**Before:**

Exception: (ClassCastException("class net.imglib2.type.logic.BitType cannot
be cast to class net.imglib2.type.logic.NativeBoolType (net.imglib2.type.logic.BitType
and net.imglib2.type.logic.NativeBoolType are in unnamed module of loader 'app')"),
ClassCastException("class net.imglib2.type.logic.BitType cannot be cast to class
net.imglib2.type.logic.NativeBoolType (net.imglib2.type.logic.BitType and
net.imglib2.type.logic.NativeBoolType are in unnamed module of loader 'app')"),
RuntimeException("java.util.concurrent.ExecutionException: java.lang.ClassCastException:
class net.imglib2.type.logic.BitType cannot be cast to class net.imglib2.type.logic.NativeBoolType
(net.imglib2.type.logic.BitType and net.imglib2.type.logic.NativeBoolType are in unnamed module
of loader 'app')"))

**After:**

Exception:
Error: Unsupported type cast via net.imglib2.util.ImgUtil.copy
    Source type: net.imglib2.type.logic.BitType
    Target type: net.imglib2.type.logic.NativeBoolType
Error: Unsupported type cast via net.imglib2.util.Images.copy
    Source type: net.imglib2.type.logic.BitType
    Target type: net.imglib2.type.logic.NativeBoolType
Error: Unsupported type cast via net.imagej.ops.copy.CopyNamespace.rai
    Source type: net.imglib2.type.logic.BitType
    Target type: net.imglib2.type.logic.NativeBoolType

src/imagej/images.py

@@ -154,7 +154,9 @@ def copy_rai_into_ndarray(
             return narr
         except JException as exc:
             # Try another method
-            failure_exceptions.append(exc)
+            failure_exceptions.append(
+                _format_copy_exception(exc.toString(), "net.imglib2.util.ImgUtil.copy")
+            )
 
     # Check imagej-common version for fast copy availability.
     imagej_common_version = sj.get_version(jc.Dataset)
@@ -167,7 +169,9 @@ def copy_rai_into_ndarray(
             return narr
         except JException as exc:
             # Try another method
-            failure_exceptions.append(exc)
+            failure_exceptions.append(
+                _format_copy_exception(exc.toString(), "net.imglib2.util.Images.copy")
+            )
 
     # Fall back to copying with ImageJ Ops's copy.rai op. In theory, Ops
     # should always be faster. But in practice, the copy.rai operation is
@@ -178,10 +182,15 @@ def copy_rai_into_ndarray(
         return
     except JException as exc:
         # Try another method
-        failure_exceptions.append(exc)
+        failure_exceptions.append(
+            _format_copy_exception(
+                exc.toString(), "net.imagej.ops.copy.CopyNamespace.rai"
+            )
+        )
 
     # Failed
-    raise Exception("Could not copy rai into ndarray", *failure_exceptions)
+    failure_msg = "\n".join(failure_exceptions)
+    raise Exception("\n" + failure_msg)
 
 
 def dtype(image_or_type) -> np.dtype:
@@ -238,3 +247,25 @@ def dtype(image_or_type) -> np.dtype:
         raise TypeError(f"Unsupported original ImageJ type: {imagej_type}")
 
     raise TypeError("Unsupported Java type: " + str(sj.jclass(image_or_type).getName()))
+
+
+def _format_copy_exception(exc: str, fun_name: str) -> str:
+    """Format copy exceptions strings.
+
+    :param exc: Exception as a String.
+    :param fun_name: Name of the function producing the exception.
+    :return: The formatted exception.
+    """
+    # format cast exception
+    m = exc.split(" ")
+    from_class = ""
+    to_class = ""
+    if m[0] == "java.lang.ClassCastException:" and "net.imglib2.util" in fun_name:
+        from_class = m[2]
+        to_class = m[8]
+    elif m[0] == "java.lang.RuntimeException:" and "net.imagej.ops" in fun_name:
+        from_class = m[4]
+        to_class = m[10]
+    msg = f"Error: Unsupported type cast via {fun_name}\n    Source type: {from_class}\n    Target type: {to_class}"
+
+    return msg