enhance avocado:utils:genio as a new utility

added utility which takes as argument a file and pattern
and return true or false respectively when pattern matches in
file or not

>>> from avocado.utils import genio
>>> genio.find_pattern("/home/praveen/file1", "praveen")
True
>>> genio.find_pattern("/home/praveen/file1", "Praveen")
False
>>> genio.find_pattern("/home/praveen/file12", "Praveen")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "avocado/utils/genio.py", line 219, in find_pattern
    % (filename, pattern))
avocado.utils.genio.GenIOError: invalid file /home/praveen/file12 to match pattern Praveen
>>>
Signed-off-by: NPraveen K Pandey <praveen@linux.vnet.ibm.com>

avocado/utils/genio.py

@@ -19,6 +19,7 @@ Avocado generic IO related functions.
 import logging
 import os
 import time
+import re
 
 from six.moves import input
 
@@ -200,3 +201,24 @@ def write_file_or_fail(filename, data):
     except OSError as details:
         raise GenIOError("The write to %s failed: %s" % (
                          filename, details))
+
+
+def find_pattern(filename,  pattern):
+    """
+    Module for match pattern in a specified file
+
+    :param filename: Path to file
+    :type filename: str
+    :param pattern: pattern that need to match in file
+    :type pattern: str
+    :return: True when pattern matches in file if not
+             retun False
+    """
+    if not os.path.isfile(filename):
+        raise GenIOError('invalid file %s to match pattern %s'
+                         % (filename, pattern))
+
+    with open(filename, 'r') as content_file:
+        if re.search(pattern, content_file.read(), re.MULTILINE):
+            return True
+    return False