avocado.utils.path: Add PathInspector class

We're planning to move away from the rule

1 test == 1 directory

In order to do that, we need to be able to tell
the difference between a dropin test (this can
be written in any language as long as it is an
executable file) and an avocado test (a python
file that contains a test class derived from
the base avocado test file).

Introduce in the path library a path inspector,
that has code to figure this out.
Signed-off-by: NLucas Meneghel Rodrigues <lmr@redhat.com>

avocado/utils/path.py

@@ -17,6 +17,10 @@ Avocado path related functions.
 """
 
 import os
+import stat
+
+PY_EXTENSIONS = ['.py']
+SHEBANG = '#!'
 
 
 def init_dir(*args):
@@ -32,3 +36,42 @@ def init_dir(*args):
     if not os.path.isdir(directory):
         os.makedirs(directory)
     return directory
+
+
+class PathInspector(object):
+
+    def __init__(self, path):
+        self.path = path
+
+    def get_first_line(self):
+        first_line = ""
+        if os.path.isfile(self.path):
+            checked_file = open(self.path, "r")
+            first_line = checked_file.readline()
+            checked_file.close()
+        return first_line
+
+    def has_exec_permission(self):
+        mode = os.stat(self.path)[stat.ST_MODE]
+        return mode & stat.S_IXUSR
+
+    def is_empty(self):
+        size = os.stat(self.path)[stat.ST_SIZE]
+        return size == 0
+
+    def is_script(self, language=None):
+        first_line = self.get_first_line()
+        if first_line:
+            if first_line.startswith(SHEBANG):
+                if language is None:
+                    return True
+                elif language in first_line:
+                    return True
+        return False
+
+    def is_python(self):
+        for extension in PY_EXTENSIONS:
+            if self.path.endswith(extension):
+                return True
+
+        return self.is_script(language='python')