Various optimizations part 1

* Configure for python3
* Update tests
* Use appropriate virtualenv
* Install nginx for the integration tests
* Try use LD_LIBRARY_PATH to find augeas shared library in snap when python-augeas is invoked
* Update travis to use build-in setup capabilities
* Update .travis.yml
* Add acme build
* Update tests
* Try more recent dist
* Update command
* Clean tests
* Add back augeas
* Add env
* Revert to last working snapcraft config
* Add a gitignore
* Reintegrate acme. Declare augeas in certbot parts
* Use release version of certbot
* Try new approach
* Fix config
* Directly install version of python-augeas from pypi
* Restart from basic
* Clone only once certbot repository. Use pinned versions of dependencies from certbot-auto.
* Try relatively to source
* Use snapcraft env variables
* Strip hashes
* Fix path
* Redefine path
* Continue to prepare the runtime
* Fix command line
* Update .travis.yml
* Add back certbot-apache
* Update snapcraft.yaml
* Build snap against the latest release of certbot

snap/snapcraft.yaml

@@ -2,6 +2,7 @@ name: certbot
 version: script
 version-script: cd parts/certbot/src && git describe|sed s/^v//
 summary: Automatically configure HTTPS using Let's Encrypt
+base: core18
 description: |
  The objective of Certbot, Let's Encrypt, and the ACME (Automated
  Certificate Management Environment) protocol is to make it possible
@@ -23,45 +24,42 @@ apps:
     command: certbot
     environment:
       PATH: "$SNAP/bin:$SNAP/usr/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games"
-      AUGEAS_LENS_LIB: $SNAP/usr/share/augeas/lenses/dist
+      AUGEAS_LENS_LIB: "$SNAP/usr/share/augeas/lenses/dist"
+      LD_LIBRARY_PATH: "$SNAP/usr/lib/x86_64-linux-gnu/:$LD_LIBRARY_PATH"
   renew:
     command: certbot -q renew
     daemon: oneshot
     environment:
       PATH: "$SNAP/bin:$SNAP/usr/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games"
       AUGEAS_LENS_LIB: $SNAP/usr/share/augeas/lenses/dist
+      LD_LIBRARY_PATH: "$SNAP/usr/lib/x86_64-linux-gnu/:$LD_LIBRARY_PATH"
     passthrough:
         # Run approximately twice a day with randomization
         timer: 00:00~24:00/2
 
 parts:
-  python-augeas:
+  acme:
     plugin: python
-    source: git://github.com/basak/python-augeas
-    source-branch: snap
-    python-version: python2
-    build-packages: [libaugeas0]
+    source: certbot
+    source-subdir: acme
+    constraints: $SNAPCRAFT_PART_SRC/constraints.txt
+    python-version: python3
   certbot:
     plugin: python
-    source: git://github.com/certbot/certbot
-    source-branch: master
-    python-version: python2
-    after: [python-augeas]
-  certbot-nginx:
-    plugin: python
-    source: git://github.com/certbot/certbot
-    source-branch: master
-    source-subdir: certbot-nginx
-    build-packages: [libaugeas-dev]
-    stage-packages: [libaugeas0]
-    after: [certbot]
-    python-version: python2
+    source: certbot
+    constraints: $SNAPCRAFT_PART_SRC/constraints.txt
+    python-version: python3
+    python-packages:
+    - acme
+    after: [acme]
   certbot-apache:
     plugin: python
-    source: git://github.com/certbot/certbot
-    source-branch: master
+    source: certbot
     source-subdir: certbot-apache
+    constraints: $SNAPCRAFT_PART_SRC/constraints.txt
+    python-version: python3
+    python-packages:
+    - certbot
     build-packages: [libaugeas-dev]
     stage-packages: [libaugeas0]
     after: [certbot]
-    python-version: python2