I seldom mess around with my productive debian 8 system, so I can't remember when or how this problem was introduced. I noticed it when trying to install openshot and got unmet dependencies (output at the end, because my problem seems to go deeper).I did apt-get update and it works as usual, no warnings or errors. But apt-get upgrade reports:Reading package lists... DoneBuilding dependency tree       Reading state information... DoneCalculating upgrade... DoneThe following packages have been kept back:  librtmp10 upgraded, 0 newly installed, 0 to remove and 1 not upgraded.Why kept back? Trying apt-get install librtmp1:Reading package lists... DoneBuilding dependency tree       Reading state information... DoneSome packages could not be installed. This may mean that you haverequested an impossible situation or if you are using the unstabledistribution that some required packages have not yet been createdor been moved out of Incoming.The following information may help to resolve the situation:The following packages have unmet dependencies: librtmp1 : Depends: libgnutls30 (>= 3.5.6) but it is not installable            Depends: libhogweed4 but it is not installable            Depends: libnettle6 but it is not installableE: Unable to correct problems, you have held broken packages.Not installable sounds nasty. But I can't remove it, because among the packages that depend on it (directly or indirecly) are basics as cmake, libre-office and kde-runtime (and blender, gimp, qemu and many others).some postings suggest to do apt-get dist-upgrade, but that does nothing:Reading package lists... DoneBuilding dependency tree       Reading state information... DoneCalculating upgrade... Done0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.One more strange observation on my manual fixing attempts doing apt-get install python-mlt it comes to very basic conflicts for libstdc++6:Reading package lists... DoneBuilding dependency tree       Reading state information... DoneSome packages could not be installed. This may mean that you haverequested an impossible situation or if you are using the unstabledistribution that some required packages have not yet been createdor been moved out of Incoming.The following information may help to resolve the situation:The following packages have unmet dependencies: python-mlt : Depends: libmlt++3 (>= 1:6.4.1) but it is not going to be installed              Depends: libmlt6 (>= 1:6.4.1) but it is not going to be installed              Depends: libstdc++6 (>= 5) but 4.9.2-10 is to be installedE: Unable to correct problems, you have held broken packages.Update: /etc/apt/sources.list:deb [arch=amd64,i386] http://ftp.de.debian.org/debian jessie main contrib non-freedeb-src http://ftp.de.debian.org/debian/ jessie maindeb [arch=amd64,i386] http://ftp2.de.debian.org/debian jessie-backports maindeb-src http://ftp2.de.debian.org/debian jessie-backports maindeb http://www.deb-multimedia.org testing main non-freeI don't remember when that multimedia testing got into it ...
Debian Jessie broken dependencies: The following packages have been kept back: librtmp1
debian;apt;dependencies
Edit your sources.list , replace testing by jessie then run:apt-get updateapt-get upgradept-get install python-mlt