Support for multi-os Python install

`/usr/bin/env` being used in scripts at the moment is not acceptable in
certain distributions. macOS system Python is generally not used by
developers in favour of Homebrew Python - this installs to
`/usr/bin/local`.

One cannot support both install locations `/usr/bin` and
`/usr/bin/local` without using `/usr/bin/env` in the shebang. To remedy
this, the Makefile resolves the shell `python` (3 first, then any) executable to
`PYTHON_CMD` and calls the scripts with this binary.

Arduino.mk

@@ -853,15 +853,15 @@ endif
 # Reset
 
 ifndef RESET_CMD
-  ARD_RESET_ARDUINO := $(shell which ard-reset-arduino 2> /dev/null)
+  ARD_RESET_ARDUINO := $(PYTHON_CMD) $(shell which ard-reset-arduino 2> /dev/null)
   ifndef ARD_RESET_ARDUINO
     # same level as *.mk in bin directory when checked out from git
     # or in $PATH when packaged
-    ARD_RESET_ARDUINO = $(ARDMK_DIR)/bin/ard-reset-arduino
+    ARD_RESET_ARDUINO = $(PYTHON_CMD) $(ARDMK_DIR)/bin/ard-reset-arduino
   endif
   ifneq (,$(findstring CYGWIN,$(shell uname -s)))
       # confirm user is using default cygwin unix Python (which uses ttySx) and not Windows Python (which uses COMx)
-      ifeq ($(shell which python),/usr/bin/python)
+      ifeq ($(PYTHON_CMD),/usr/bin/python)
         RESET_CMD = $(ARD_RESET_ARDUINO) $(ARD_RESET_OPTS) $(DEVICE_PATH)
       else
         RESET_CMD = $(ARD_RESET_ARDUINO) $(ARD_RESET_OPTS) $(call get_monitor_port)

Common.mk

@@ -98,3 +98,24 @@ ifeq ($(CURRENT_OS),WINDOWS)
         echo $(error On Windows, ARDUINO_DIR and other defines must use forward slash and not contain spaces, special characters or be cygdrive relative)
     endif
 endif
+
+########################################################################
+# System Python
+
+ifndef PYTHON_CMD
+    # try for Python 3 first
+    PYTHON_CMD := $(shell which python3 2> /dev/null)
+    ifdef PYTHON_CMD
+        $(call show_config_variable,PYTHON_CMD,[AUTODETECTED])
+    else
+        # fall-back to any Python
+        PYTHON_CMD := $(shell which python 2> /dev/null)
+        ifdef PYTHON_CMD
+            $(call show_config_variable,PYTHON_CMD,[AUTODETECTED])
+        else
+            echo $(error "Unable to find system Python! Utility scipts won't work. Override this error by defining PYTHON_CMD")
+        endif
+    endif
+else
+    $(call show_config_variable,PYTHON_CMD,[USER])
+endif

HISTORY.md

@@ -33,6 +33,7 @@ I tried to give credit whenever possible. If I have missed anyone, kindly add it
 - New: Updated Arch instructions. (https://github.com/Akram-Chehaima)
 - New: Add support for Robotis OpenCR 1.0 boards.
 - New: Build the ArduinoCore API
+- New: Support for Python 3 and multi-os Python installation using new PYTHON_CMD variable.
 
 ### 1.6.0 (2017-07-11)
 - Fix: Allowed for SparkFun's weird usb pid/vid submenu shenanigans (issue #499). (https://github.com/sej7278)

README.md

@@ -123,10 +123,11 @@ On Arch:
 sudo pacman -S python-pyserial
 ```
 
-On Mac using MacPorts:
+On macOS using Homebrew (one can install to System Python but this is not recommend or good practice):
 
 ```sh
-sudo port install py27-serial
+brew install python
+pip3 install pyserial
 ```
 
 On Windows:

arduino-mk-vars.md

@@ -134,6 +134,22 @@ RESET_CMD = $(HOME)/gertduino/reset
 
 ----
 
+### PYTHON_CMD
+
+**Description:**
+
+Path to Python binary. Requires pyserial module installed. Makefile will error if unable to auto-find as utility scripts will not work. To override this, give it an empty define.
+
+**Example:**
+
+```Makefile
+PYTHON_CMD = /usr/bin/python3
+```
+
+**Requirement:** *Optional*
+
+----
+
 ## Arduino IDE variables
 
 ### ARDUINO_DIR

bin/ard-reset-arduino

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/python3
 
 from __future__ import print_function
 import serial

bin/ardmk-init

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/python3
 """
 Arduino-mk Makefile and project initialiser
 

bin/robotis-loader

@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/python3
 
 # This script sends a program on a robotis board (OpenCM9.04 or CM900)
 # using the robotis bootloader (used in OpenCM IDE)