Update Travis config to build with ESP-IDF v3.3. (DavidAntliff#2)

* Update Travis config to build with ESP-IDF v3.3.

* Update Travis config to build with ESP-IDF v3.3.

* Update Travis config to build with ESP-IDF v3.3.

* Update Travis config to build with Python 3.

* Update Travis config to build with Python3.

* Update Travis config to build with Python3.

* Add support for concurrent make.

* Shallow submodule checkout.

Author: DavidAntliff

.travis.yml

@@ -1,14 +1,18 @@
-sudo: false
+dist: bionic
+env:
+  global:
+    # Set Python 3.7.1 as the default python
+    - PATH=/opt/python/3.7.1/bin:$PATH
+    - MAKEFLAGS="-j 2"
+
 language: bash
-os:
-  - linux
 
 addons:
   apt:
     packages:
       - gperf
-      - python
-      - python-serial
+      - python3
+      - python3-pip
 
 before_install:
   # Save path to the git respository
@@ -29,9 +33,11 @@ install:
   # Make xtensa-esp32-elf available for all terminal sessions
   - export PATH=$PATH:$HOME/esp/xtensa-esp32-elf/bin
   # Get ESP-IDF from github
-  - git clone --recursive --branch release/v3.0 https://github.com/espressif/esp-idf.git
+  - git clone --recursive --branch v3.3 --single-branch --shallow-submodules https://github.com/espressif/esp-idf.git
   # Set the path to ESP-IDF directory
   - export IDF_PATH=~/esp/esp-idf
+  # Install python dependencies
+  - pip install --user --requirement $IDF_PATH/requirements.txt
 
 script:
   # Go back to the git repository
@@ -40,4 +46,3 @@ script:
   - make defconfig
   # Build project from the git repository
   - make
-