patman: Detect missing tools and report them

When tools are needed but not present, at present we just get an error
which can be confusing for the user. Try to be helpful by reporting the
tool as missing and suggesting a possible remedy.

Also update the Run() method to support this.
Signed-off-by: NSimon Glass <sjg@chromium.org>

tools/patman/tools.py

@@ -22,6 +22,10 @@ chroot_path = None
 # Search paths to use for Filename(), used to find files
 search_paths = []
 
+# Tools and the packages that contain them, on debian
+packages = {
+    'lz4': 'liblz4-tool',
+    }
 
 def PrepareOutputDir(dirname, preserve=False):
     """Select an output directory, ensuring it exists.
@@ -128,8 +132,31 @@ def Align(pos, align):
 def NotPowerOfTwo(num):
     return num and (num & (num - 1))
 
+def PathHasFile(fname):
+    """Check if a given filename is in the PATH
+
+    Args:
+        fname: Filename to check
+
+    Returns:
+        True if found, False if not
+    """
+    for dir in os.environ['PATH'].split(':'):
+        if os.path.exists(os.path.join(dir, fname)):
+            return True
+    return False
+
 def Run(name, *args):
-    command.Run(name, *args, cwd=outdir)
+    try:
+        return command.Run(name, *args, cwd=outdir, capture=True)
+    except:
+        if not PathHasFile(name):
+            msg = "Plesae install tool '%s'" % name
+            package = packages.get(name)
+            if package:
+                 msg += " (e.g. from package '%s')" % package
+            raise ValueError(msg)
+        raise
 
 def Filename(fname):
     """Resolve a file path to an absolute path.