Notify when attempting to overwrite active python

User is now notified if we are in python mode and try to build
environment when targeting our active python directory.

See related Fiji commit:
fiji/fiji@f492fcb

Author: hinerm

src/main/java/org/scijava/plugins/scripting/python/RebuildEnvironment.java

@@ -75,7 +75,24 @@ public class RebuildEnvironment implements Command {
 	@Override
 	public void run() {
 		final File backupDir = new File(targetDir.getPath() + ".old");
+		// Prevent rebuilding the environment currently in use by pyimagej
 		if (targetDir.exists()) {
+			String cfgPythonDir = System.getProperty("scijava.python.dir", "");
+			if (cfgPythonDir != null && !cfgPythonDir.isEmpty()) {
+				// Normalize both paths for comparison
+				String targetPath = targetDir.getAbsolutePath().replace("\\", "/");
+				String cfgPath = cfgPythonDir.replace("\\", "/");
+				if (targetPath.endsWith(cfgPath)) {
+					String msg = "You cannot rebuild the environment currently being used by pyimagej (" + cfgPythonDir + ").\n" +
+						"Please select a different target directory, or restart in Java mode.";
+					if (uiService != null) {
+						uiService.showDialog(msg, "Cannot Rebuild Active Environment", DialogPrompt.MessageType.ERROR_MESSAGE);
+					} else {
+						log.error(msg);
+					}
+					return;
+				}
+			}
 			boolean confirmed = true;
 			if (uiService != null) {
 				String msg =