Revert "Removing LANG env var (#570)"

This reverts commit 0b9aee9.

Author: tianon

3.10/alpine3.14/Dockerfile

@@ -19,6 +19,10 @@ FROM buildpack-deps:{{ env.variant }}
 # ensure local python is preferred over distribution python
 ENV PATH /usr/local/bin:$PATH
 
+# http://bugs.python.org/issue19846
+# > At the moment, setting "LANG=C" on a Linux system *fundamentally breaks Python 3*, and that's not OK.
+ENV LANG C.UTF-8
+
 # runtime dependencies
 {{ if is_alpine then ( -}}
 RUN set -eux; \