IMPALA-11398: Ignore Flake8 rule E126

In Impala we use 2 spaces for indentation, however for continuation
lines we use 4 spaces (or more if it makes the code look nicer).
This violates Flake8's rule E126 which generates noise during
code reviews.

This patch adds E126 to the list of ignored rules.

Change-Id: I1beb76feed90ee524d5c2c27487561891958e54c
Reviewed-on: http://gerrit.cloudera.org:8080/18836
Reviewed-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>
Reviewed-by: Michael Smith <michael.smith@cloudera.com>
Tested-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>
diff --git a/setup.cfg b/setup.cfg
index 242078b..3552dd9 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -15,13 +15,13 @@
 # specific language governing permissions and limitations
 # under the License.
 [flake8]
-# E121,E125,E127,E128: ignored to allow some of the more common idioms for multi-line
-#                      statement indentation used in the Impala code.
+# E121,E125,E126,E127,E128: ignored to allow some of the more common idioms for multi-line
+#                           statement indentation used in the Impala code.
 # W503: ignored to allow line breaks before binary operators, as is becoming standard:
 #       https://github.com/python/peps/commit/7690a00d478866
 # E701: ignored to allow if statement body on same line as conditional
 # https://pycodestyle.readthedocs.io/en/latest/intro.html#error-codes
-ignore = E121,E125,E127,E128,W503,E701
+ignore = E121,E125,E126,E127,E128,W503,E701
 # Change from default to conform to Apache Impala line length.
 max-line-length = 90
 # Impala style guide uses 2-space indents.