theming-controlpanel trouble with themes

[VerSooSet]

What I did:

I have selected a plone theme (zip file) to upload.
the Diazo theme engine opened and I pressed the button "Back to the control panel"

What I expect to happen

Error about what wrong at new zip theme.

What actually happened:

New theme is not placed to list of themes below. Its not set too. But text are printing: Error There were errors

I tried again. Expecting web theme engine would open, but it didn't. Besides that text waited me again.
screenshots serie

Some other zip themes loaded fine and placed to theme list finally. No text appeared.

This theme are reproduce a problem:

1. plonetheme.business_casual
2. plonetheme.clean_blog

At sources of addon plone.app.theming I found
src/plone/app/theming/browser/controlpanel.py .

Error are apeeared as exception each time when function update(self) throwing self.errors.

Look at the condition :
if 'form.button.Import' in form

Each have text "Error. There were errors" placed before:

no rules file,
invalid zip,
already installed.

What version of Plone/ Addons I am using:

Plone 5.0.4.

[pigeonflight]

I tried to reproduce the bug on Plone 5.0.4 but was not able to.
I downloaded the zip file for Plone Business Casual from https://github.com/collective/plonetheme.business_casual/blob/master/plonetheme.business_casual.zip?raw=true
and Clean Blog https://github.com/collective/plonetheme.clean_blog/blob/master/plonetheme.clean_blog.zip?raw=true

Both installed without issue.

[VerSooSet]

Thank for attention to issue!
I think I have caught a #107 with invisible theme. Thats why web interface isn't open.

Through this, I had a chance to see how duplicate defense works. Sad the duplicate condition is not active. In fact i have theme at site resources but is not seen in manager. Duplicate defense must to inform me like I has seen it

u"This theme is already installed. Select "
u"'Replace existing theme' and re-upload to "
u"replace it."

I confirm non informative message when reloaded again to site theme contained manifest file.

[tkimnguyen]

In #107 I added a comment to show where we can avoid the problem of the uploaded theme not having a manifest.cfg