Schemas missing - Unity Tweak Tool

Question

I understand this is very similar to this question and this one, but none of the answers there have worked for me. When trying to install the packages mentioned in those questions, apt-get throws up the following error message:

Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies.
 unity-webapps-service : Depends: webapp-container
E: Unable to correct problems, you have held broken packages.

When I try to install the dependencies mentioned there, I just find more and more dependencies. Synaptic Package Manager gives error messages when I select 'Fix Broken Packages'. How can I fix this?

Thanks in advance, and please comment if you need more information.

UPDATE: Running apt-cache policy webapp-container unity-webapps-service gave the following result:

webapp-container:
  Installed: (none)
  Candidate: 0.23+14.04.20140428-0ubuntu1
  Version table:
     0.23+14.04.20140428-0ubuntu1 0
        500 http://gb.archive.ubuntu.com/ubuntu/ trusty-updates/main amd64 Packages
     0.23+14.04.20140414-0ubuntu1 0
        500 http://gb.archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages
unity-webapps-service:
  Installed: (none)
  Candidate: 2.5.0~+14.04.20140409-0ubuntu1
  Version table:
     2.5.0~+14.04.20140409-0ubuntu1 0
        500 http://gb.archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages
        100 /var/lib/dpkg/status

UPDATE 2: Version information:

LSB Version:    core-2.0-amd64:core-2.0-noarch:core-3.0-amd64:core-3.0-noarch:core-3.1-amd64:core-3.1-noarch:core-3.2-amd64:core-3.2-noarch:core-4.0-amd64:core-4.0-noarch:core-4.1-amd64:core-4.1-noarch:security-4.0-amd64:security-4.0-noarch:security-4.1-amd64:security-4.1-noarch
Distributor ID: Ubuntu
Description:    Ubuntu 14.04.2 LTS
Release:    14.04
Codename:   trusty

UPDATE 3: When trying to install unity-webapps-service using aptitude instead of apt-get:

The following NEW packages will be installed:
  liboxideqt-qmlplugin{a} liboxideqtcore0{a} liboxideqtquick0{ab} 
  libqt5feedback5{a} libqt5multimedia5{ab} libqt5organizer5{ab} 
  libqt5positioning5{ab} libunity-webapps0{a} 
  qtdeclarative5-dialogs-plugin{ab} 
  qtdeclarative5-privatewidgets-plugin{ab} 
  qtdeclarative5-qtfeedback-plugin{a} 
  qtdeclarative5-ubuntu-ui-extras-browser-plugin{a} 
  qtdeclarative5-ubuntu-ui-toolkit-plugin{ab} unity-webapps-qml{a} 
  unity-webapps-service webapp-container{ab} webbrowser-app{ab} 
0 packages upgraded, 17 newly installed, 0 to remove and 0 not upgraded.
Need to get 26.6 MB of archives. After unpacking 103 MB will be used.
The following packages have unmet dependencies:
 webapp-container : Depends: qtdeclarative-abi-5-2-1 which is a virtual package.
 libqt5organizer5 : Depends: qtbase-abi-5-2-1 which is a virtual package.
 qtdeclarative5-dialogs-plugin : Depends: qtbase-abi-5-2-1 which is a virtual package.
                                 Depends: qtdeclarative-abi-5-2-1 which is a virtual package.
 webbrowser-app : Depends: qtdeclarative-abi-5-2-1 which is a virtual package.
 qtdeclarative5-privatewidgets-plugin : Depends: qtbase-abi-5-2-1 which is a virtual package.
 libqt5multimedia5 : Depends: qtbase-abi-5-2-1 which is a virtual package.
 libqt5positioning5 : Depends: qtbase-abi-5-2-1 which is a virtual package.
 liboxideqtquick0 : Depends: qtdeclarative-abi-5-2-1 which is a virtual package.
 qtdeclarative5-ubuntu-ui-toolkit-plugin : Depends: qtbase-abi-5-2-1 which is a virtual package.
                                           Depends: qtdeclarative-abi-5-2-1 which is a virtual package.
The following actions will resolve these dependencies:

      Keep the following packages at their current version:           
1)      liboxideqt-qmlplugin [Not Installed]                          
2)      liboxideqtcore0 [Not Installed]                               
3)      liboxideqtquick0 [Not Installed]                              
4)      libqt5feedback5 [Not Installed]                               
5)      libqt5multimedia5 [Not Installed]                             
6)      libqt5organizer5 [Not Installed]                              
7)      libqt5positioning5 [Not Installed]                            
8)      libunity-webapps0 [Not Installed]                             
9)      qtdeclarative5-dialogs-plugin [Not Installed]                 
10)     qtdeclarative5-privatewidgets-plugin [Not Installed]          
11)     qtdeclarative5-qtfeedback-plugin [Not Installed]              
12)     qtdeclarative5-ubuntu-ui-extras-browser-plugin [Not Installed]
13)     qtdeclarative5-ubuntu-ui-toolkit-plugin [Not Installed]       
14)     unity-webapps-qml [Not Installed]                             
15)     unity-webapps-service [Not Installed]                         
16)     webapp-container [Not Installed]                              
17)     webbrowser-app [Not Installed]                                



Accept this solution? [Y/n/q/?]

UPDATE 4: The output of sudo apt-get install qtdeclarative-abi-5-2-1:

Reading package lists... Done
Building dependency tree       
Reading state information... Done
Package qtdeclarative-abi-5-2-1 is a virtual package provided by:
  libqt5qml5 5.2.1-3ubuntu15.1 [Not candidate version]
  libqt5qml5 5.2.1-3ubuntu15 [Not candidate version]

E: Package 'qtdeclarative-abi-5-2-1' has no installation candidate

The output of sudo apt-get install unity-webapp-container:

Reading package lists... Done
Building dependency tree       
Reading state information... Done
E: Unable to locate package unity-webapp-container

UPDATE 5: Output of apt-cache policy libqt5qml5:

libqt5qml5:
  Installed: 5.3.0-3ubuntu13~trusty1
  Candidate: 5.3.0-3ubuntu13~trusty1
  Version table:
 *** 5.3.0-3ubuntu13~trusty1 0
        500 http://ppa.launchpad.net/mscore-ubuntu/mscore-stable/ubuntu/ trusty/main amd64 Packages
        100 /var/lib/dpkg/status
     5.2.1-3ubuntu15.1 0
        500 http://gb.archive.ubuntu.com/ubuntu/ trusty-updates/main amd64 Packages
     5.2.1-3ubuntu15 0
        500 http://gb.archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages

Output of sudo apt-get install webapp-container:

Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies.
 webapp-container : Depends: qtdeclarative-abi-5-2-1
                    Depends: unity-webapps-qml but it is not going to be installed
                    Depends: webbrowser-app (= 0.23+14.04.20140428-0ubuntu1)
E: Unable to correct problems, you have held broken packages.

run & post - apt-cache policy webapp-container unity-webapps-service — doug, Jun 22 '15 at 17:56
Well then try to specifically install unity-webapps-service as in sudo apt-get install unity-webapps-service (- are you running Ubuntu 14.04 or something else? - lsb_release -a — doug, Jun 23 '15 at 00:31
@doug Trying to install unity-webapps-service gives me the error at the top of my question! And yes, I'm running Ubuntu 14.04.2 LTS. — thesdog, Jun 23 '15 at 16:12
Try switching to the Main server in Software & Updates, then try again. if it fails please post here or in a pastebin the complete terminal output start to finish — doug, Jun 23 '15 at 16:28
@doug Switching to the main server has seemed to make no difference at all. Again, apt-get gives exactly the same error message when trying to install unity-webapps-service. Here it is in a pastebin: http://paste.ubuntu.com/11763213/ — thesdog, Jun 23 '15 at 16:54
Very odd, try sudo apt-get clean && sudo apt-get update Then ck. this package, apt-cache policy libunity-webapps0 if avail. see if it will install — doug, Jun 23 '15 at 17:03
@doug libunity-webapps0 isn't installed, and I can't install it either. Similar error messages. — thesdog, Jun 23 '15 at 17:13
Can you install anything? (pick something from software-center). If so then install aptitude and use it instead of apt-get, usually aptitude is a bit more verbose. — doug, Jun 23 '15 at 20:07
@doug SuperTux 2 installed fine from the Ubuntu Software Centre. I've installed aptitude and this is what it says when I run sudo aptitude install unity-webapps-service: http://paste.ubuntu.com/11764338/ — thesdog, Jun 23 '15 at 20:35
@doug said in the chat: It's that ppa you are using that has updated some qt libs that aren't compatible with the Ubuntu packages you are trying to install. So either live without them & the tweak package or use ppa-purge on the ppa. — thesdog, Jul 10 '15 at 20:42
[Edit] your question and add the output of sudo apt-get install qtdeclarative-abi-5-2-1 and sudo apt-get install unity-webapp-container in exact this order and give me a ping with @A.B. — A.B., Aug 28 '15 at 13:17
Please answer my comment, otherwise your points were in vain. — A.B., Aug 31 '15 at 14:00
@A.B. Sorry, I didn't have access to my computer yesterday. I'll try and answer your comment as soon as possible. — thesdog, Aug 31 '15 at 17:17
If as mentioned you don't wish to purge that ppa then try extracting the schema from unity-webapps-service package, placing in /usr/share/glib-2.0/schemas/ , recompiling glib schemas & see if unity tweak suffers in use. Was in the 2nd of your links - http://askubuntu.com/questions/449943/unity-tweak-tool-fails-to-start-with-the-error-com-canonical-unity-webapps-sche answer by jackyzy823 — doug, Aug 31 '15 at 20:06
@doug What exactly does purging the PPA do? I'm happy to do it as long as it doesn't have any negative effects... Also, how do I extract the schema? Sorry, I'm still somewhat a noob! — thesdog, Sep 01 '15 at 21:53
could you remind me which ppa, I can't find the chat room so have forgotten. If you purge the ppa then you'll lose whatever you got from enabling it in the first place. If you want try the extract end around I'd prefer ubuntu forums as it's more interactive. You could always summerize an answer here if it proves suitable — doug, Sep 02 '15 at 01:55
@doug Found the chat room - I had to “show frozen rooms". https://chat.stackexchange.com/transcript/25123/2015/6/23 — thesdog, Sep 02 '15 at 10:28

A.B. · Accepted Answer · 2015-09-02T14:11:59.177

I'll risk it and leave a response.

A main problem seems to be the PPA ppa:mscore-ubuntu/mscore-stable. With this PPA you can't use the needed version of libqt5qml5

Therefore remove the PPA with the following command.

sudo ppa-purge ppa:mscore-ubuntu/mscore-stable

After that

sudo apt-get install -f

and finally

sudo apt-get install unity-webapps-service

Where is the problem?

The command apt-cache policy libqt5qml5 returns the following. The PPA ppa:mscore-ubuntu/mscore-stable installs a newer version (5.3.0) for libqt5qml5 but qtdeclarative-abi-5-2-1 needs exact version 5.2.1.

libqt5qml5:
  Installed: 5.3.0-3ubuntu13~trusty1
  Candidate: 5.3.0-3ubuntu13~trusty1
  Version table:
 *** 5.3.0-3ubuntu13~trusty1 0
        500 http://ppa.launchpad.net/mscore-ubuntu/mscore-stable/ubuntu/ trusty/main amd64 Packages
        100 /var/lib/dpkg/status
     5.2.1-3ubuntu15.1 0
        500 http://gb.archive.ubuntu.com/ubuntu/ trusty-updates/main amd64 Packages
     5.2.1-3ubuntu15 0
        500 http://gb.archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages

Side effects

Purging the PPA downgrades the packages installed by the PPA. If a downgrade isn't possible, because a package only exists in this PPA, the package will be removed. The configuration files of the package still exists in your system after the removal.

Comments are not for extended discussion; this conversation has been moved to chat. — Seth, Sep 02 '15 at 22:42

Schemas missing - Unity Tweak Tool

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