Merge pull request #372 from pre-commit/dont_crash_on_not_found_exe

Don't crash when an executable is not found

pre_commit/parse_shebang.py

@@ -12,6 +12,10 @@ from pre_commit import five
 printable = frozenset(string.printable)
 
 
+class ExecutableNotFoundError(OSError):
+    pass
+
+
 def parse_bytesio(bytesio):
     """Parse the shebang from a file opened for reading binary."""
     if bytesio.read(2) != b'#!':
@@ -70,7 +74,9 @@ def normexe(orig_exe):
     if os.sep not in orig_exe:
         exe = find_executable(orig_exe)
         if exe is None:
-            raise OSError('Executable {0} not found'.format(orig_exe))
+            raise ExecutableNotFoundError(
+                'Executable `{0}` not found'.format(orig_exe),
+            )
         return exe
     else:
         return orig_exe

pre_commit/util.py

@@ -181,23 +181,26 @@ def cmd_output(*cmd, **kwargs):
         for key, value in kwargs.pop('env', {}).items()
     ) or None
 
-    cmd = parse_shebang.normalize_cmd(cmd)
-
-    popen_kwargs.update(kwargs)
-    proc = __popen(cmd, **popen_kwargs)
-    stdout, stderr = proc.communicate()
-    if encoding is not None and stdout is not None:
-        stdout = stdout.decode(encoding)
-    if encoding is not None and stderr is not None:
-        stderr = stderr.decode(encoding)
-    returncode = proc.returncode
+    try:
+        cmd = parse_shebang.normalize_cmd(cmd)
+    except parse_shebang.ExecutableNotFoundError as e:
+        returncode, stdout, stderr = (-1, e.args[0].encode('UTF-8'), b'')
+    else:
+        popen_kwargs.update(kwargs)
+        proc = __popen(cmd, **popen_kwargs)
+        stdout, stderr = proc.communicate()
+        if encoding is not None and stdout is not None:
+            stdout = stdout.decode(encoding)
+        if encoding is not None and stderr is not None:
+            stderr = stderr.decode(encoding)
+        returncode = proc.returncode
 
     if retcode is not None and retcode != returncode:
         raise CalledProcessError(
             returncode, cmd, retcode, output=(stdout, stderr),
         )
 
-    return proc.returncode, stdout, stderr
+    return returncode, stdout, stderr
 
 
 def rmtree(path):