diff --git a/Makefile b/Makefile
index 148ca66fa..326f8f581 100644
--- a/Makefile
+++ b/Makefile
@@ -134,7 +134,7 @@ compressed: $(ALL_COMPRESSED_FILES)
 check_compress_tool:
 ifdef MISSING_ZOPFLI
   ifdef MISSING_OPTIPNG
-	$(error "neither $(ZOPFLIPNG) nor $(OPTIPNG) is available")
+	$(error "neither $(ZOPFLIPNG) nor $(OPTIPNG) is available. For installation instructions, see README.md")
   else
 	@echo "using $(OPTIPNG)"
   endif
@@ -197,6 +197,11 @@ else
 	@$(ZOPFLIPNG) -y "$<" "$@" 1> /dev/null 2>&1
 endif
 
+check-virtual-env:
+ifeq (${VIRTUAL_ENV},)
+	@echo Please start your virtual environment, and run: "'pip install -r requirements.txt'".
+	@false
+endif
 
 # Make 3.81 can endless loop here if the target is missing but no
 # prerequisite is updated and make has been invoked with -j, e.g.:
@@ -214,7 +219,7 @@ endif
 	@rm -f "$@"
 	ttx "$<"
 
-$(EMOJI).ttf: $(EMOJI).tmpl.ttf $(EMOJI_BUILDER) $(PUA_ADDER) \
+$(EMOJI).ttf: check-virtual-env $(EMOJI).tmpl.ttf $(EMOJI_BUILDER) $(PUA_ADDER) \
 	$(ALL_COMPRESSED_FILES) | check_vs_adder
 	@$(PYTHON) $(EMOJI_BUILDER) $(SMALL_METRICS) -V $< "$@" "$(COMPRESSED_DIR)/emoji_u"
 	@$(PYTHON) $(PUA_ADDER) "$@" "$@-with-pua"
diff --git a/README.md b/README.md
index 1883dd933..6943d49b8 100644
--- a/README.md
+++ b/README.md
@@ -2,16 +2,29 @@
 # Noto Emoji
 Color and Black-and-White Noto emoji fonts, and tools for working with them.
 
+## Prerequisites
+Building Noto Color Emoji requires:
+- Python 3
+- [pkg-config](https://www.freedesktop.org/wiki/Software/pkg-config/)
+- [pngquant](https://pngquant.org/)
+- Either [zopflipng](https://github.com/google/zopfli) or [optipng](http://optipng.sourceforge.net/). Zopflipng is better (about 5-10%) but much slower.
+
 ## Building NotoColorEmoji
+This project uses a virtual environment to manage dependencies. Use the following steps to get up and running.
 
-Building NotoColorEmoji currently requires a Python 2.x wide build.  To build
-the emoji font you will require a few files from nototools.  Clone a copy from
-https://github.com/googlei18n/nototools and either put it in your PYTHONPATH or
-use 'python setup.py develop' ('install' currently won't fully install all the
-data used by nototools).  You will also need fontTools, get it from
-https://github.com/behdad/fonttools.git.
+Create a virtual environment called `noto-emoji-env`:
 
-Then run make.  NotoColorEmoji is the default target.  It's suggested to use -j,
+	python3 -m venv noto-emoji-env
+
+Activate the virtual environment:
+
+	source noto-emoji-env/bin/activate
+
+Install the Python requirements with:
+	
+	pip install -r requirements.txt
+
+Then run `make`.  NotoColorEmoji is the default target.  It's suggested to use -j,
 especially if you are using zopflipng for compression.  Intermediate products
 (compressed image files, for example) will be put into a build subdirectory; the
 font will be at the top level.
diff --git a/add_emoji_gsub.py b/add_emoji_gsub.py
index 9f578a302..9f1c40366 100755
--- a/add_emoji_gsub.py
+++ b/add_emoji_gsub.py
@@ -18,13 +18,11 @@
 
 __author__ = "roozbeh@google.com (Roozbeh Pournader)"
 
-
 import sys
 
 from fontTools import agl
-from fontTools import ttLib
 from fontTools.ttLib.tables import otTables
-
+from fontTools import ttLib
 from nototools import font_data
 
 
diff --git a/requirements.txt b/requirements.txt
new file mode 100644
index 000000000..9748ccfa8
--- /dev/null
+++ b/requirements.txt
@@ -0,0 +1,2 @@
+fonttools>=4.7.0
+-e git://github.com/googlefonts/nototools.git#egg=master
\ No newline at end of file