Fix newline in tag value cause partial commit (#716)

When a tag value contains newline(\n), the request sent to db would be splitted
into two parts and the first part would fail to write to db but the second
woudl be succeed. The reason is that before sending we do serialization
(make_lines) the _escape_tag method in line_protocol.py
won't handle it well, we need somehow more specific on newline instead of
only handling escape character (\)

Author: syhan

influxdb/line_protocol.py

@@ -54,6 +54,8 @@ def _escape_tag(tag):
         ",", "\\,"
     ).replace(
         "=", "\\="
+    ).replace(
+        "\n", "\\n"
     )
 
 

influxdb/tests/test_line_protocol.py

@@ -115,6 +115,27 @@ def test_make_lines_unicode(self):
             'test,unicode_tag=\'Привет!\' unicode_val="Привет!"\n'
         )
 
+    def test_tag_value_newline(self):
+        """Test make lines with tag value contains newline."""
+        data = {
+            "tags": {
+                "t1": "line1\nline2"
+            },
+            "points": [
+                {
+                    "measurement": "test",
+                    "fields": {
+                        "val": "hello"
+                    }
+                }
+            ]
+        }
+
+        self.assertEqual(
+            line_protocol.make_lines(data),
+            'test,t1=line1\\nline2 val="hello"\n'
+        )
+
     def test_quote_ident(self):
         """Test quote indentation in TestLineProtocol object."""
         self.assertEqual(