scripts: runners: handle uninstalled dependencies

Catch ImportError whenever a non-standard module import fails from any
runners that do one. Complain at runtime about it if the user actually
needs the runner.

Signed-off-by: Martí Bolívar <marti.bolivar@nordicsemi.no>

scripts/west_commands/runners/canopen_program.py

@@ -7,11 +7,15 @@
 import argparse
 import os
 
-import canopen
-from progress.bar import Bar
-
 from runners.core import ZephyrBinaryRunner, RunnerCaps
 
+try:
+    import canopen
+    from progress.bar import Bar
+    MISSING_REQUIREMENTS = False
+except ImportError:
+    MISSING_REQUIREMENTS = True
+
 # Default Python-CAN context to use, see python-can documentation for details
 DEFAULT_CAN_CONTEXT = 'default'
 
@@ -38,6 +42,11 @@ class CANopenBinaryRunner(ZephyrBinaryRunner):
     def __init__(self, cfg, node_id, can_context=DEFAULT_CAN_CONTEXT,
                  program_number=1, confirm=True,
                  confirm_only=True, timeout=10):
+        if MISSING_REQUIREMENTS:
+            raise RuntimeError('one or more Python dependencies were missing; '
+                               "see the getting started guide for details on "
+                               "how to fix")
+
         super(CANopenBinaryRunner, self).__init__(cfg)
         self.bin_file = cfg.bin_file
         self.confirm = confirm

scripts/west_commands/runners/core.py

@@ -313,7 +313,13 @@ class ZephyrBinaryRunner(abc.ABC):
     3. Give your runner's name to the Zephyr build system in your
        board's board.cmake.
 
-    Some advice on input and output:
+    Additional advice:
+
+    - If you need to import any non-standard-library modules, make sure
+      to catch ImportError and defer complaints about it to a RuntimeError
+      if one is missing. This avoids affecting users that don't require your
+      runner, while still making it clear what went wrong to users that do
+      require it that don't have the necessary modules installed.
 
     - If you need to ask the user something (e.g. using input()), do it
       in your create() classmethod, not do_run(). That ensures your

scripts/west_commands/runners/openocd.py

@@ -5,7 +5,11 @@
 '''Runner for openocd.'''
 
 from os import path
-from elftools.elf.elffile import ELFFile
+
+try:
+    from elftools.elf.elffile import ELFFile
+except ImportError:
+    ELFFile = None
 
 from runners.core import ZephyrBinaryRunner
 
@@ -106,6 +110,9 @@ class OpenOcdBinaryRunner(ZephyrBinaryRunner):
 
     def do_run(self, command, **kwargs):
         self.require(self.openocd_cmd[0])
+        if ELFFile is None:
+            raise RuntimeError(
+                'elftools missing; please "pip3 install elftools"')
 
         self.cfg_cmd = []
         if self.openocd_config is not None: