Clearer AdbCommandFailedError messages

Makes error messages clearer by making it more explicit that
the failure happened when running a specific command on a
device; and, although adb is the means by which commands are
run, it is itself not suspected of causing the failure.

BUG=442252

Review URL: https://codereview.chromium.org/800383002

Cr-Commit-Position: refs/heads/master@{#309838}

build/android/pylib/device/adb_wrapper.py

@@ -222,12 +222,12 @@ def Shell(self, command, expect_status=0, timeout=_DEFAULT_TIMEOUT,
         status = int(output[output_end+1:])
       except ValueError:
         logging.warning('exit status of shell command %r missing.', command)
-        raise device_errors.AdbCommandFailedError(
-            args, output, device_serial=self._device_serial)
+        raise device_errors.AdbShellCommandFailedError(
+            command, output, status=None, device_serial=self._device_serial)
       output = output[:output_end]
       if status != expect_status:
-        raise device_errors.AdbCommandFailedError(
-            args, output, status, self._device_serial)
+        raise device_errors.AdbShellCommandFailedError(
+            command, output, status=status, device_serial=self._device_serial)
     return output
 
   def Ls(self, path, timeout=_DEFAULT_TIMEOUT, retries=_DEFAULT_RETRIES):

build/android/pylib/device/device_errors.py

@@ -27,25 +27,41 @@ def __init__(self, message, device_serial=None):
 class AdbCommandFailedError(CommandFailedError):
   """Exception for adb command failures."""
 
-  def __init__(self, cmd, output, status=None, device_serial=None):
-    self.cmd = cmd
+  def __init__(self, args, output, status=None, device_serial=None,
+               message=None):
+    self.args = args
     self.output = output
     self.status = status
-    message = []
-    if self.cmd[0] == 'shell':
-      assert len(self.cmd) == 2
-      message.append('adb shell command %r failed with' % self.cmd[1])
-    else:
-      command = ' '.join(cmd_helper.SingleQuote(arg) for arg in self.cmd)
-      message.append('adb command %r failed with' % command)
-    if status:
-      message.append(' exit status %d and' % self.status)
+    if not message:
+      adb_cmd = ' '.join(cmd_helper.SingleQuote(arg) for arg in self.args)
+      message = ['adb %s: failed ' % adb_cmd]
+      if status:
+        message.append('with exit status %s ' % self.status)
+      if output:
+        message.append('and output:\n')
+        message.extend('- %s\n' % line for line in output.splitlines())
+      else:
+        message.append('and no output.')
+      message = ''.join(message)
+    super(AdbCommandFailedError, self).__init__(message, device_serial)
+
+
+class AdbShellCommandFailedError(AdbCommandFailedError):
+  """Exception for shell command failures run via adb."""
+
+  def __init__(self, command, output, status, device_serial=None):
+    self.command = command
+    message = ['shell command run via adb failed on the device:\n',
+               '  command: %s\n' % command]
+    message.append('  exit status: %s\n' % status)
     if output:
-      message.append(' output:\n')
-      message.extend('> %s\n' % line for line in output.splitlines())
+      message.append('  output:\n')
+      message.extend('  - %s\n' % line for line in output.splitlines())
     else:
-      message.append(' no output')
-    super(AdbCommandFailedError, self).__init__(''.join(message), device_serial)
+      message.append("  output: ''\n")
+    message = ''.join(message)
+    super(AdbShellCommandFailedError, self).__init__(
+      ['shell', command], output, status, device_serial, message)
 
 
 class CommandTimeoutError(BaseError):

build/android/pylib/device/device_utils_test.py

@@ -191,10 +191,10 @@ def setUp(self):
         self.adb, default_timeout=10, default_retries=0)
     self.watchMethodCalls(self.call.adb, ignore=['GetDeviceSerial'])
 
-  def ShellError(self, output=None, exit_code=1):
+  def ShellError(self, output=None, status=1):
     def action(cmd, *args, **kwargs):
-      raise device_errors.AdbCommandFailedError(
-          cmd, output, exit_code, str(self.device))
+      raise device_errors.AdbShellCommandFailedError(
+          cmd, output, status, str(self.device))
     if output is None:
       output = 'Permission denied\n'
     return action