link: add WriteFile method.

BUG=none
TEST=make test; make lint

Change-Id: Idc18639ea4a1ed89d862462490435ef80457fe3c
diff --git a/graphyte/link.py b/graphyte/link.py
index f6964c3..64b018c 100644
--- a/graphyte/link.py
+++ b/graphyte/link.py
@@ -7,6 +7,8 @@
 import subprocess
 import tempfile
 
+from . import utils
+
 CalledProcessError = subprocess.CalledProcessError
 
 MODULE_PATH_MAPPING = {
@@ -141,6 +143,18 @@
     except CalledProcessError:
       return None
 
+  def WriteFile(self, path, content):
+    """Writes some content into file on DUT.
+
+    Args:
+      path: A string for file path on DUT.
+      content: A string to be written into file.
+    """
+    with utils.UnopenedTemporaryFile() as temp_path:
+      with open(temp_path, 'w') as f:
+        f.write(content)
+      self.Push(temp_path, path)
+
 
 def _GetLinkClass(class_name):
   """Loads and returns a class object specified from the arguments.