diff --git a/docker/mace-dev/Dockerfile b/docker/mace-dev/Dockerfile
index 9669613d66d26f4d9d4e28ff7fde5faf7167bfa3..23c98b3915b2c6d401ef22b5d61bb7316b646d4a 100644
--- a/docker/mace-dev/Dockerfile
+++ b/docker/mace-dev/Dockerfile
@@ -82,7 +82,6 @@ ENV LINARO_ARM_LINUX_GNUEABIHF /opt/gcc-linaro-7.3.1-2018.05-x86_64_arm-linux-gn
 ENV LINARO_AARCH64_LINUX_GNU /opt/gcc-linaro-7.3.1-2018.05-x86_64_aarch64-linux-gnu
 ENV PATH /opt/protoc-3.6.1/bin:${PATH}
 
-
 RUN pyenv install 2.7.12
 RUN pyenv global 2.7.12
 RUN pip install -i http://mirrors.aliyun.com/pypi/simple/ --trusted-host mirrors.aliyun.com --upgrade pip setuptools
@@ -112,6 +111,3 @@ RUN pip install -i http://mirrors.aliyun.com/pypi/simple/ --trusted-host mirrors
 
 RUN pip install -i http://mirrors.aliyun.com/pypi/simple/ --trusted-host mirrors.aliyun.com \
     cpplint==1.4.4
-
-# Restore to python3
-RUN pyenv global 3.6.3
diff --git a/docs/Makefile b/docs/Makefile
index 391e8520160b5362d71b4b5c9f4d1f39b057746a..10559b41b6b92c00e4a7b6785d6fa987e0c7518e 100644
--- a/docs/Makefile
+++ b/docs/Makefile
@@ -17,4 +17,5 @@ help:
 # Catch-all target: route all unknown targets to Sphinx using the new
 # "make mode" option.  $(O) is meant as a shortcut for $(SPHINXOPTS).
 %: Makefile
-	@$(SPHINXBUILD) -M $@ "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)
\ No newline at end of file
+	pyenv local 3.6.3
+	@$(SPHINXBUILD) -M $@ "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)
diff --git a/tools/device.py b/tools/device.py
index 00f3aa372096cdaefd724cbd90682c5324861600..22648ad9a0806ca914717778865ba9453ef91f8f 100644
--- a/tools/device.py
+++ b/tools/device.py
@@ -244,8 +244,6 @@ class DeviceWrapper:
                 stderr=subprocess.PIPE,
                 stdout=subprocess.PIPE)
             out, err = p.communicate()
-            out = str(out, encoding='utf-8')
-            err = str(err, encoding='utf-8')
             self.stdout = err + out
             six.print_(self.stdout)
             six.print_("Running finished!\n")