.travis.yml: fix package install on PPA builder

.travis.yml

@@ -130,15 +130,8 @@ jobs:
         - ubuntu-ppa
       git:
         submodules: false # avoid cloning ethereum/tests
-      addons:
-        apt:
-          packages:
-            - devscripts
-            - debhelper
-            - dput
-            - fakeroot
-            - python-bzrlib
-            - python-paramiko
+      before_install:
+        - sudo -E apt-get -yq --no-install-suggests --no-install-recommends install devscripts debhelper dput fakeroot python-bzrlib python-paramiko
       script:
         - echo '|1|7SiYPr9xl3uctzovOTj4gMwAC1M=|t6ReES75Bo/PxlOPJ6/GsGbTrM0= ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEA0aKz5UTUndYgIGG7dQBV+HaeuEZJ2xPHo2DS2iSKvUL4xNMSAY4UguNW+pX56nAQmZKIZZ8MaEvSj6zMEDiq6HFfn5JcTlM80UwlnyKe8B8p7Nk06PPQLrnmQt5fh0HmEcZx+JU9TZsfCHPnX7MNz4ELfZE6cFsclClrKim3BHUIGq//t93DllB+h4O9LHjEUsQ1Sr63irDLSutkLJD6RXchjROXkNirlcNVHH/jwLWR5RcYilNX7S5bIkK8NlWPjsn/8Ua5O7I9/YoE97PpO6i73DTGLh5H9JN/SITwCKBkgSDWUt61uPK3Y11Gty7o2lWsBjhBUm2Y38CBsoGmBw==' >> ~/.ssh/known_hosts
         - go run build/ci.go debsrc -upload ethereum/ethereum -sftp-user geth-ci -signer "Go Ethereum Linux Builder <geth-ci@ethereum.org>"