diff --git a/.gitignore b/.gitignore
index a5cc017b1..8307d40fe 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,3 +2,4 @@ __pycache__/
 *.pyc
 waveflag
 build/
+venv/
diff --git a/Makefile b/Makefile
index 3e1f820ee..ca6b7e34b 100644
--- a/Makefile
+++ b/Makefile
@@ -24,11 +24,8 @@ PNGQUANTFLAGS = --speed 1 --skip-if-larger --quality 85-95 --force
 BODY_DIMENSIONS = 136x128
 IMOPS := -size $(BODY_DIMENSIONS) canvas:none -compose copy -gravity center
 
-# zopflipng is better (about 5-10%) but much slower.  it will be used if
-# present.  pass ZOPFLIPNG= as an arg to make to use optipng instead.
-
 ZOPFLIPNG = zopflipng
-OPTIPNG = optipng
+TTX = ttx
 
 EMOJI_BUILDER = third_party/color_emoji/emoji_builder.py
 # flag for emoji builder.  Default to legacy small metrics for the time being.
@@ -83,6 +80,23 @@ SELECTED_FLAGS = AC AD AE AF AG AI AL AM AO AQ AR AS AT AU AW AX AZ \
 	ZA ZM ZW \
         GB-ENG GB-SCT GB-WLS
 
+ifeq (,$(shell which $(ZOPFLIPNG)))
+  ifeq (,$(wildcard $(ZOPFLIPNG)))
+    MISSING_ZOPFLI = fail
+  endif
+endif
+
+ifndef VIRTUAL_ENV
+  MISSING_VENV = fail
+endif
+
+ifeq (, $(shell which $(VS_ADDER)))
+  MISSING_PY_TOOLS = fail
+endif
+ifeq (, $(shell which $(TTX)))
+  MISSING_PY_TOOLS = fail
+endif
+
 ALL_FLAGS = $(basename $(notdir $(wildcard $(FLAGS_SRC_DIR)/*.png)))
 
 FLAGS = $(SELECTED_FLAGS)
@@ -91,7 +105,11 @@ FLAG_NAMES = $(FLAGS:%=%.png)
 FLAG_FILES = $(addprefix $(FLAGS_DIR)/, $(FLAG_NAMES))
 RESIZED_FLAG_FILES = $(addprefix $(RESIZED_FLAGS_DIR)/, $(FLAG_NAMES))
 
+ifndef MISSING_PY_TOOLS
 FLAG_GLYPH_NAMES = $(shell $(PYTHON) flag_glyph_name.py $(FLAGS))
+else
+FLAG_GLYPH_NAMES = 
+endif
 RENAMED_FLAG_NAMES = $(FLAG_GLYPH_NAMES:%=emoji_%.png)
 RENAMED_FLAG_FILES = $(addprefix $(RENAMED_FLAGS_DIR)/, $(RENAMED_FLAG_NAMES))
 
@@ -103,23 +121,6 @@ ALL_NAMES = $(EMOJI_NAMES) $(RENAMED_FLAG_NAMES)
 ALL_QUANTIZED_FILES = $(addprefix $(QUANTIZED_DIR)/, $(ALL_NAMES))
 ALL_COMPRESSED_FILES = $(addprefix $(COMPRESSED_DIR)/, $(ALL_NAMES))
 
-# tool checks
-ifeq (,$(shell which $(ZOPFLIPNG)))
-  ifeq (,$(wildcard $(ZOPFLIPNG)))
-    MISSING_ZOPFLI = fail
-  endif
-endif
-
-ifeq (,$(shell which $(OPTIPNG)))
-  ifeq (,$(wildcard $(OPTIPNG)))
-    MISSING_OPTIPNG = fail
-  endif
-endif
-
-ifeq (, $(shell which $(VS_ADDER)))
-  MISSING_ADDER = fail
-endif
-
 
 emoji: $(EMOJI_FILES)
 
@@ -133,22 +134,16 @@ quantized: $(ALL_QUANTIZED_FILES)
 
 compressed: $(ALL_COMPRESSED_FILES)
 
-check_compress_tool:
+check_tools:
 ifdef MISSING_ZOPFLI
-  ifdef MISSING_OPTIPNG
-	$(error "neither $(ZOPFLIPNG) nor $(OPTIPNG) is available")
-  else
-	@echo "using $(OPTIPNG)"
-  endif
-else
-	@echo "using $(ZOPFLIPNG)"
+	$(error "Missing $(ZOPFLIPNG). Try 'brew install zopfli' (Mac) or 'sudo apt-get install zopfli' (linux)")
 endif
-
-check_vs_adder:
-ifdef MISSING_ADDER
-	$(error "$(VS_ADDER) not in path, run setup.py in nototools")
+ifdef MISSING_VENV
+		$(error "Please start your virtual environment, and run: "'pip install -r requirements.txt'")
+endif
+ifdef MISSING_PY_TOOLS
+		$(error "Missing tools; run: "'pip install -r requirements.txt' in your virtual environment")
 endif
-
 
 $(EMOJI_DIR) $(FLAGS_DIR) $(RESIZED_FLAGS_DIR) $(RENAMED_FLAGS_DIR) $(QUANTIZED_DIR) $(COMPRESSED_DIR):
 	mkdir -p "$@"
@@ -192,12 +187,8 @@ $(QUANTIZED_DIR)/%.png: $(RENAMED_FLAGS_DIR)/%.png | $(QUANTIZED_DIR)
 $(QUANTIZED_DIR)/%.png: $(EMOJI_DIR)/%.png | $(QUANTIZED_DIR)
 	@($(PNGQUANT) $(PNGQUANTFLAGS) -o "$@" "$<"; case "$$?" in "98"|"99") echo "reuse $<";cp $< $@;; *) exit "$$?";; esac)
 
-$(COMPRESSED_DIR)/%.png: $(QUANTIZED_DIR)/%.png | check_compress_tool $(COMPRESSED_DIR)
-ifdef MISSING_ZOPFLI
-	@$(OPTIPNG) -quiet -o7 -clobber -force -out "$@" "$<"
-else
+$(COMPRESSED_DIR)/%.png: $(QUANTIZED_DIR)/%.png | check_tools $(COMPRESSED_DIR)
 	@$(ZOPFLIPNG) -y "$<" "$@" 1> /dev/null 2>&1
-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.:
@@ -216,7 +207,8 @@ endif
 	ttx "$<"
 
 $(EMOJI).ttf: check_sequence $(EMOJI).tmpl.ttf $(EMOJI_BUILDER) $(PUA_ADDER) \
-	$(ALL_COMPRESSED_FILES) | check_vs_adder
+	$(ALL_COMPRESSED_FILES) | check_tools
+
 	@$(PYTHON) $(EMOJI_BUILDER) $(SMALL_METRICS) -V $< "$@" "$(COMPRESSED_DIR)/emoji_u"
 	@$(PYTHON) $(PUA_ADDER) "$@" "$@-with-pua"
 	@$(VS_ADDER) -vs 2640 2642 2695 --dstdir '.' -o "$@-with-pua-varsel" "$@-with-pua"
@@ -238,5 +230,5 @@ clean:
 .SECONDARY: $(EMOJI_FILES) $(FLAG_FILES) $(RESIZED_FLAG_FILES) $(RENAMED_FLAG_FILES) \
   $(ALL_QUANTIZED_FILES) $(ALL_COMPRESSED_FILES)
 
-.PHONY:	clean flags emoji renamed_flags quantized compressed check_compress_tool
+.PHONY:	clean flags emoji renamed_flags quantized compressed check_tools
 
diff --git a/README.md b/README.md
index 1883dd933..01401661d 100644
--- a/README.md
+++ b/README.md
@@ -2,25 +2,36 @@
 # 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/)
+- [zopflipng](https://github.com/google/zopfli)
+
 ## 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.
+```shell
+# make sure you have the Prerequisites
 
-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.
+# create & activate a virtual environment
+python3 -m venv venv
+source venv/bin/activate
+
+# install python requirements
+pip install -r requirements.txt
+
+time make -j
+```
+
+Intermediate products (compressed image files, for example) will be put into a build subdirectory; the font will be at the top level.
 
 ## Using NotoColorEmoji
 
 NotoColorEmoji uses the CBDT/CBLC color font format, which is supported by Android
 and Chrome/Chromium OS.  Windows supports it starting with Windows 10 Anniversary
-Update in Chome and Edge.  On macOS, only Chrome supports it, while on Linux it will
+Update in Chrome and Edge.  On macOS, only Chrome supports it, while on Linux it will
 support it with some fontconfig tweaking, see [issue #36](https://github.com/googlei18n/noto-emoji/issues/36). Currently we do not build other color font formats.
 
 ## Color emoji assets
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/flag_glyph_name.py b/flag_glyph_name.py
index e5ce40c20..84cfeb64b 100755
--- a/flag_glyph_name.py
+++ b/flag_glyph_name.py
@@ -22,7 +22,11 @@ __author__ = 'roozbeh@google.com (Roozbeh Pournader)'
 import re
 import sys
 
-import add_emoji_gsub
+try:
+  import add_emoji_gsub
+except ImportError as e:
+    print(e, file=sys.stderr)
+    sys.exit('Python environment is not setup right')
 
 def two_letter_code_to_glyph_name(region_code):
     return 'u%04x_%04x' % (
diff --git a/requirements.txt b/requirements.txt
new file mode 100644
index 000000000..4cda58f53
--- /dev/null
+++ b/requirements.txt
@@ -0,0 +1,2 @@
+fonttools>=4.7.0
+notofonttools>=0.2.4
\ No newline at end of file