Improve copy exception formatter

This time I'm more clever and look for the keywords "cannot" and "cast"
in the exception string. Perhaps this will be more tolerant of slight
variations of the exception stirng than relying on hard coded indices.

src/imagej/images.py

@@ -257,15 +257,11 @@ def _format_copy_exception(exc: str, fun_name: str) -> str:
     :return: The formatted exception.
     """
     # format cast exception
+    exc = str(exc)
     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
+    if "cannot be cast to" in exc:
+        from_class = m[m.index("cannot") - 1]
+        to_class = m[m.index("cast") + 3]
+        return f"Error: Unsupported type cast via {fun_name}\n    Source type: {from_class}\n    Target type: {to_class}"
+    else:
+        return exc