pmrule.py: add FILE_CONTENTS rule

Signed-off-by: Andrew Gregory <andrew.gregory.8@gmail.com>
Signed-off-by: Allan McRae <allan@archlinux.org>

test/pacman/README

@@ -303,6 +303,7 @@ its DEPENDS field.
 
 	. FILE rules
 
+  FILE_CONTENTS=path/to/file|contents
   FILE_EXIST=path/to/file
   FILE_EMPTY=path/to/file
   FILE_MODIFIED=path/to/file

test/pacman/pmrule.py

@@ -120,6 +120,12 @@ def check(self, test):
                 if not (os.path.isfile(filename)
                         and os.path.getsize(filename) == 0):
                     success = 0
+            elif case == "CONTENTS":
+                try:
+                    with open(filename, 'r') as f:
+                        success = f.read() == value
+                except:
+                    success = 0
             elif case == "MODIFIED":
                 for f in test.files:
                     if f.name == key: