Issue2920

Running on Mac OS X 10.15.7. Creating a standalone jar file. 
➜ ~ /usr/bin/java -jar Downloads/jython-installer-2.7.2.jar 
Exception in thread "Thread-4" org.python.util.install.InstallerException: Error accessing jar file
	at org.python.util.install.JarInstaller.inflate(JarInstaller.java:177)
	at org.python.util.install.ProgressPage.activate(ProgressPage.java:84)
	at org.python.util.install.AbstractWizardPage.doActivate(AbstractWizardPage.java:41)
	at org.python.util.install.AbstractWizard.showActivePage(AbstractWizard.java:414)
	at org.python.util.install.AbstractWizard.next(AbstractWizard.java:319)
	at org.python.util.install.AbstractWizard.gotoNextPage(AbstractWizard.java:215)
	at org.python.util.install.AbstractWizardValidator.fireValidationSucceeded(AbstractWizardValidator.java:78)
	at org.python.util.install.AbstractWizardValidator.access100ドル(AbstractWizardValidator.java:6)
	at org.python.util.install.AbstractWizardValidator$ValidatorThread.run(AbstractWizardValidator.java:16)
Caused by: java.util.zip.ZipException: duplicate entry: module-info.class
	at java.util.zip.ZipOutputStream.putNextEntry(ZipOutputStream.java:232)
	at java.util.jar.JarOutputStream.putNextEntry(JarOutputStream.java:109)
	at org.python.util.install.StandalonePackager.addJarFile(StandalonePackager.java:92)
	at org.python.util.install.JarInstaller.inflate(JarInstaller.java:163)
	... 8 more
➜ ~ /usr/bin/java -version
java version "1.8.0_181"
Java(TM) SE Runtime Environment (build 1.8.0_181-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.181-b13, mixed mode)

You tried the obvious things I suppose? (Permissions on the JAR, incomplete or corrupt download, reputable source.) Does this give you a plausible contents list:
jar -tf Downloads\jython-installer-2.7.2.jar >tf.txt
Starts:
META-INF/
META-INF/MANIFEST.MF
Demo/
Demo/applet/
Demo/applet/deprecated/
Demo/awt/
Ends:
tests/java/org/python/tests/props/Readonly.java
tests/java/org/python/util/InterpreterTest.java
tests/java/org/python/util/jythonTest.java
tests/java/org/python/util/jythonTestPlain.java
I don't have a Mac, but a fresh download of the installer worked for me on Windows. Did it get anywhere at all? Obviously it got as far as running the installer classes, but did you get the dialogues, licence, place to install, etc.? Was this during the mass unpacking that follows?

module-info.class in the traceback makes me think this could have something do do with https://bugs.jython.org/issue2924.