I've built spark-2.0-preview (8f5a04b) with scala-2.10 using the following

./dev/change-version-to-2.10.sh
./dev/make-distribution.sh -DskipTests -Dzookeeper.version=3.4.5 -Dcurator.version=2.4.0 -Dscala-2.10 -Phadoop-2.6  -Pyarn -Phive

and then ran the following code in a pyspark shell

from pyspark.sql import SparkSession
from pyspark.sql.types import IntegerType, StructField, StructType
from pyspark.sql.functions import udf
from pyspark.sql.types import Row
spark = SparkSession.builder.master('local[4]').appName('2.0 DF').getOrCreate()
add_one = udf(lambda x: x + 1, IntegerType())
schema = StructType([StructField('a', IntegerType(), False)])
df = spark.createDataFrame([Row(a=1),Row(a=2)], schema)
df.select(add_one(df.a).alias('incremented')).collect()

This never returns with a result.